Index

Introduction of Programming

Directory Structure of C Language

Integrated Development Environment

Data Types.

printf , scanf Functions ,getch function.

Constants , Variables , Keywords , Operators , Escape Sequence, Format Specifier.

Decision Making In C Using if statement & switch case default.

Loop.

User Defined Functions.

Preprocessor Directives.

Pointer.

Introduction to Programming Languages

1

Programming languages are classified into two different types. Procedural and Non-Procedural

Procedural languages specify how something is accomplished. Non Procedural languages specify what is accomplished without going into detail of how.

The difference b/w Procedural and Non-Procedural language is illustrated in following example:

Procedural language : Like I am sit on a Taxi and give directives to Taxi Driver….The directions might go as : Drive 600 yards forward, Turn right then Drive 300 yards forward then Stop.

Non-Procedural language: You would simply tell the Driver what you want. “Take me to Tariq Road”

Topic 2 Introduction to C - Language

C is a programming language developed at AT & T’s Bell laboratories of USA in 1972. It was designed and written by a man named Dennis Ritchie. C is so popular b/c it is reliable, simple and easy to use.

Where C Stands

C is often classified a middle-level language. C is b/w these two categories i.e High level language and Low level language.

Learning Language

Communication with a computer involves speaking the language the computer understand. Learning any Computer language is like the same as we learn other spoken languages.

If we want to learn English we first learn alphabets or characters used in the language, then word and then form a sentence and sentence are combined to form a paragraph. Learning C is similar.

Steps in learning English:

Alphabets Words Sentence Paragraph

Steps in learning C:

Alphabets Constant Instructions ProgramDigits VariablesSpecial Symbols Keywords

C Character Set

Alphabets A,B,………….Y,ZA,b,…………..y,z

Digits 0,1,2,3,4,5,6,7,8,9 Special Symbols ~ ! @ # % ^ ` & * ( ) _ - + = | \ [ ] { } : ; “ ‘ < > ? /

2

Directory Structure of CC :\TC BIN ( Bin Folder contains TC.exe file to execute IDE)

INCLUDE ( Header Files is like text files …….extension .h) LIB ( Routines for performing specific task…extension .lib)

Don’t change the name of the sub-directories.

Executable Files Executable files are stored in the sub directory BIN. The most important exe. File is TC.exe.

Library Files If a programmer uses a function such as printf() to display text on the screen, the code to create the display is

contained in a library file. A library file has unique characteristics: only those parts that are necessary will be linked to a program, not

the whole file.

Concepts of Header Files Header Files : The sub directory called INCLUDE contains header files. These files also called “Include files” are text files like the one you generate with word processor. Header files can be combined with your program before it is compiled, in a same way that a typist can insert

a standard heading in a business letter. Each Header file has a .h file extension. Header files serve several purposes. You can place statements in your program listing that are not program

code but instead message to the compiler. These messages called compiler directives, can tell the compiler such things as the definition of words and phrases used in your program.

Some useful compiler directives have been grouped together in header files, which can be included in your source code of your program before it goes to the compiler.

IDE (Integrated Development Environment) & Command line Development

Turbo C features an IDE, which provides a platform to C programmers. There is another completely different way to develop C programs in Turbo C. This is a traditional command – line system, in which editing, compiling, linking, debugging and executing are performed in Dos environment.

Two different language translators Programs are used to translate High level languages :1. Compilers 2. Interpreters 3. Assembler

Compiler: A compiler translates a whole program, called the source code, into machine language all at one time before the program is executed.

Once converted, the program is stored in machine readable form called the object code.

Like: ABC COMPILING 100101000010

SOURCE COMPILER OBJECTCODE CODE

The Object code can be immediately executed anytime thereafter.

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Interpreter: A Interpreter translates a program into a machine language one line at a time, executing each line of the program after it is translated.

With most Interpreters, the machine readable form is not stored in main memory or on a secondary storage medium. Therefore, the program must be interpreted each time it is executed.

Making an EXE. File After you’ve written the source file for your program, you need to turn it into an executable file. Compiling: The program you typed is understandable to human being (at least if they know C).

However, it is not understandable to the microprocessor in your computer. There must be two versions of the program. The one you type which is Source file and the machine language

version, which is called the exe file (also called binary file). The Compiler which is a part of the IDE, translates this source code into machine language.

Linking The text editor produces .c source file, which go to the compiler, which produces .obj files, which go to the

linker, which produces .exe executable files.

Stdio.h

Myprog.c MyProg.obj Myprog.exe

Compiler Linker

Cs.lib

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IDE (Integrated Development Environment) & Command line Development

Turbo C features an IDE, which provides a platform to C programmers. There is another completely different way to develop C programs in Turbo C. This is a traditional command – line system, in which editing, compiling, linking, debugging and executing are performed in Dos environment.

IDE : It’s also referred to as the Programmer’s Platform. It is a screen display with windows and Pull-down menus.IDE provides all necessary operations for the development of your C Program, including editing, compiling, linking, and Program execution. You can even debug your program within the IDE.

Basic Structure of C ProgramLearning C, as it true with any language, is a largely a matter of practice.

Void main(void){

Printf(“Sadequain”);}

Function Definition: All C Programs are divided into units called “Functions”. No matter how many functions there are in C program, main( ) is the one to which the control is passed from the operating System, when the program is run, it is the first function to execute. The word “void” preceding “main” specifies that the function main( ) will not return a value. The second “void”,

in parentheses ------ ( ), specifies that the function takes no argument.

Conclusion: C program consists of functions. The main( ) function is the one to which control is passed when the program is executed.

Function Define: Our program begins the way all C functions do with a name followed by parentheses. This signals the compiler that a function is being defined.

Delimiter (Draws a boundary)…{ }……”{“ The Opening Brace indicates that the opening the block of code and ending Brace “}” terminates the block of code.

Statement Terminator: A statement in C is terminated with a semicolon ( ; ). Semicolon terminates the line. Each instruction in a C is written as a separate statement.

Structure of a C Program

Function Name one statement

Opening Brace to void main(void)delimit body of function

{printf(“ Sadequain “); semicolon to terminate

} each program statement

closing brace to delimit body of function

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This entire program consistsOf a function called main( )

Function Basics: Function is always in small case. No space b/w function name and parenthesis…..like printf ( ) is wrong. If you are using INPUT and OUTPUT function you have to INCLUDE header file….#include <stdio.h>

and #include <conio.h>. Function always return a value.

Exploring the printf( ) function The general form of printf( ) statement is …..printf(“ <format String> “ , list of variables); The printf( ) is a very powerful and versatile function. printf( ) is a output function.

Printing Numbers in printf( ) function: The printf( ) function using a unique format for printing constants and variables.

Like: format specifierprintf(“ This is a number two : %d”, 2);

Output: This is a number two : 2

Why was the digit 2 printed, and what effect does the %d have. String on the left……..and value on the right. The two arguments are separated by a comma.

Format Specifier:The format specifiers tells printf( ) where to put a value in a string and what format to use in printing the value. %d tells printf( ) to print the value 2 as decimal integar. Other specifier could be used for the number 2. Like %f

could cause the 2 to be printed as a floating point number.

Printing Strings:

Using the format specifier we can print constants as well as numbers….like:

Printf(“ I am %s and I am %d years old”,”Any Name”,25);

left side Right side

Scanf( ) Function: scanf ( ) is an input function. The scanf( ) function can accept input to several variable at once. The scanf( ) function use ampersand ( & ) preceding the variable names used as arguments.

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“Fundamentals of C Program”Constant: A constant is the quantity/value that doesn’t change. This value can be stored at a location in the memory of the computer. int num=1; Variable: Variable may be the most fundamental aspect of any computer language. A variable is a space in the computer’s memory set aside for a certain kind of data and given a name for easy reference.

Variable are used so that the same space in memory can hold different values at different times.

Rules for Variable Names

A Variable name is any combination of 1 to 8 alphabets, digits or underscore. The first character in the variable name must be an alphabet. No commas and space are allowed within a variable name & No special symbol other than underscore can be used in variable

name.

Variable Definition:

int num; is an example of variable definition. In a C program all variables must be defined. If you have more than one variable of same type, you can define them

all with one type name, separating the variables name with commas. Any variable used in a program must be declared before using it in any statement. When you define variable, the compiler sets aside an appropriate amount of memory to store that variable.

Defining and Declaring Variable: Variable definition specify the name and type of variable, and also set aside memory space for the variable. A variable declaration in contrast specifies the variable’s name and data type, but doesn’t set aside any memory for the variable. In most cases the word “Declaration” is used for both meanings.

Initializing Variable: It’s possible to combine a variable definition with an assignment operator so that a variable is given a value at the same time it’s defined……like

int num = 5; float num1 = 10.5;

Keywords:Keywords are the words whose meaning has already been explained to the C compiler (to the Computer).The Keywords cannot be used as variable names b/c if we do so we are trying to assign a new meaning to the keyword. It’s safer not to mix up the variable name and the keywords.

There are only 32 keywords available in C some of them are …….void, if, else, switch, case, default do, for, while, float, int, short, long, signed, unsigned….etc etc.

Operators: Operators are words or symbols that cause a program to do something to variable. There are many kinds of operators we’ll mention the most common one. Arithmetic and Relational operators and Increment and Decrement operators.

1. Arithmetic Operators........ ( +, - , * , / , % )2. Relational Operators…( <, >, <=, >=, ==, !=) which is (less than, greater than, less than equal to, not equal to)3. Logical Operators………...( &&, ||, !) which is (AND, OR, !)

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Arithmetic Operator: Precedence Operator Description 1st * / % Multiplication, division, remainder

2nd + - Addition, subtraction

3rd = Assignment

Note : The fact that (*) and (/) have a higher precedence than (+) and (-). Remainder operator is used to find the remainder when one number is divided by another.

Escape Sequences: The symbol ( \ ) backslash is considered an escape character. The tab and new line are the most often used escape sequence.

\n Newline ( for new line)\t Tab ( moves next 8 space wide field )\b Backspace ( moves the cursor one space left )\’ Single quote ( print single quote)\” Double quote ( print double quote)\\ Backslash ( print backslash )

Format Specifiers: we use format specifier ( such as %d or %c ) is used to control what format will be used by printf( ) function to print out a particular variable.

%c To print single character %s To print String%d To print signed decimal integer%u To print unsigned decimal integer%f To print floating point%l (% L) Prefix used with %d %u to specify long integer ….like ( %ld, %lu)

Data TypeNumeric Data

500 500.00 5002

Hole Decimal Scientific Number Number

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Data Type: Note short integer are the same as integer.

More on Data Types

Integer, long and short:Integers always occupies 2 Bytes in memory with a range of (32767 to -32768). Remember that out of the 2 Bytes use to store an integer, the highest bit ( 16th bit) is used to store the sign of the integer. This bit is ( 1) if the number is negative (-ve) and 0 when the number is positive (+ve). C offers a variation in integer data type that is called long integer value. The long integer occupy 4 Byte in memory and use long prior to integer in declaration like:

long int num;long int num=10;

The range of value that we can hold in long integer will expand tremendously.

In fact short is nothing but our ordinary integer, which we are using all the time without knowing that it was a short integer.

Integer, signed and unsigned:If we know in advance that a value stored in a given integer will always be positive, so we can use:

unsigned int;With such a declaration the range of integer value will shift from the range

32767 32768 65535

Unsigned almost double the size of the value that it can hold and reserve the same 2 Bytes. Unsigned integer is nothing but a short unsigned integer.

Chars, signed and unsigned:The way there is a signed and unsigned integer similarly there are signed and unsigned chars. A signed char is same as our ordinary char and has a range from (-128 to 127) where as an unsigned char has a

range from 0 to 255. 128 127

255 Floats and Double:

Data Type Range Byte Format

Signed charunsigned char

short signed intshort unsigned int

long signed intlong unsigned int

floatdouble

-128 to 1270 to 255

-32768 to +327680 to 65535

-2147483648 to +21474836470 to 4294967295

10-38 to 1038

10-138 to 10 138

11224448

%c%c%d%u%ld%lu%f%lf

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Float occupies 4 Bytes in memory and can range from 10-38 to 1038 whereas double data type occupies 8 Bytes in memory and has a range from 10308 to 10-308 .A variable of double can be declared as:

double num; Decision Making in C:

Up to now we have used sequenced control structure in which the various steps are executed sequencly i.e in the same order in which they appear in the program.Computer languages can perform different sets of actions depending on the circumstances. C has 3 major decision-making structure.

1. if statement2. if-else statement and3. switch statements

How to use if statement:

C uses the keyword “ if ” for basic decision making statement. The if statement is similar to the while . Without any operator, we cannot apply more than one condition. If you use only one statement after condition, then braces{ } sign is optional.

if( This Condition is True) execute this statement;

If the condition is true, then the statement is executed otherwise not. Relational Operators (= =, ! =, <, >, <=, >=) allow us to compare two values. Note that (=) is used for assignment, whereas (= =) is used for comparison of two quantities.

Relational Operator Conditional expression

if (char= = ‘y’)printf(“You type y”); Terminating semicolon

Structure of if statement Keyword Body of if statement

In the while statement, if the condition is true, the statement in the body of the loop will be executed over and over until the condition becomes false: In “if “ statement they will be executed only once.

The && and || operators allow two or more conditions to be combined in an if statement.

The if-else statementWhen the test expression is true, the statement will execute in the body of if statement. It does nothing when it’s false. We can execute a group of statement if and only if the test expression is not true.

This is a purpose of the else statement.

Condition expression Body of if statement keyword

if (char= = ‘y’) keyword printf(“You type y”);

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elseprintf(“\nYou did not type y.”);

Body of else statement Logical Operators: ( && , || , ! ). They are composed of double symbols ( || ), ( &&). Logical Operators have a lower precedence than the relational operators….such as ( = = ). The relational operators

are evaluated first then the logical operators. Logical Operators are always evaluated from left to right……….

if( a<b && b<c )…..a<b will be evaluated first.

The switch statement: The switch statement is similar to else-if statement but it shows clearer format. The control statement which allow us to make decision from a number of choices is called switch…..or switch-case-default.

main( ){

int i = 2; clrscr( ); integer expression

switch( i )keyword {

case 1:printf(“ I am in case 1 \n”);break;

case 2:printf(“ I am in case 2 \n”);break;

default:printf(“ I am in default \n”);

}}

Tips of switch:1. You can place cases in any order you like.2. You can also allowed to use char values in case and switch.3. Multiple statements can easily executed in each case.4. If we have no default case, then the program will continue with the next instruction ( if any ) that follows the

control structure.5. Is switch a replacement for if.

Yes ……because it offers a better way of writing programs as compared to if. No …….because in certain situations we are left no choice but to use if. The disadvantage of switch is that one cannot use case like that……..case i<=20.

6. We can only use integer or a char in case. float is not allowed.

The advantage of switch over if is that ….switch looks more structured and manageable than if.

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LoopThe program that we have developed so far used either sequential or a decision control structure. The ability to perform a set of instruction repeatedly. It means we can repeat some portion of the program either a specified number of times or until a particular condition is being satisfied. This repetitive operation is done through a loop control structure.

We can use three methods to repeat a part of a program.1. Using a for loop.2. Using a while loop.3. Using a do-while loop.

The for loop: It’s most popular looping control. The for loop specify three things about a loop in a single line.

1. Setting a loop counter to an initial value.2. Testing the loop counter.3. Increasing / Decreasing the value of loop counter each time the program within the loop has been executed.

Structure of for loop: no semicolon

here

for( initialize expression ; test expression ; increment/decrement expression)

keyword

semicolon semicolon

Body of the for loop: The statement in for loop is terminated with a semicolon, where as the for with the loop expression is not. That is because the entire combination of the for keyword, the loop expression and the statement constituting the body of the loop are considered to be a single C statement.

int i ;

for( i=0; i<=10; i++)printf(“%d”,i);

Operation of for loop: First the initializing expression is executed, then the test expression is checked. If the test expression is false to begin with, the body of the loop will not be executed at all. If the condition is true, the body of the loop is executed and following that, the increment expression is executed. The loop will continue to run until the test expression becomes false……..count becomes 10……at which time the loop will end.

C permits flexibility in the writing of the for loop. For instance…..more than one expression can be used for the initialize expression and for the increment expression by placing comma b/w them. So that several variables can be initialized and incremented at once.

Braces { } will be used when we use more than one statement in the body of for loop.

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The while loop: The second kind of loop structure available in C is the while loop.

Structure of while loop:int count=0;

loop expression

while( count<10) keyword {

printf(“%d”,count);count++;}

The initializing is now included in a variable declaration or The loop variable count is initialized outside the loop in the declaration like…………….int count=0;

When the loop is first entered, the condition (count<10) is tested. If it’s false, the loop terminates. If it’s true, the body of the loop is executed.

Increment of the expression can be perform in the body of while loop (count is incremented by the ++ operator).

The do while loop: The last of the three loops in C is do while loop.

The loop is very similar to the while loop----the difference is that in the do loop the test condition is evaluated after the loop is executed, rather than before.

Structure of do while loop: keyword

do{

countl++; Body of loopprintf(“%d”, count);

}

while(count<10); semicolon

keyword loop expression

The important thing in this loop is that, unlike for and while loops, is terminated with a semicolon. The body of the loop is first executed, then the test condition is checked, if the test condition is true, the loop is

repeated, if it is false loop terminates. The important point to notice is that the body of the loop will always be executed at least once, since the test

condition is not checked until the end of the loop.

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getch( ), getche( ) getchar( ) gets( ) : You need to press Enter key in scanf( ) function, we don’t need to press Enter key in getch function. Both purpose is Input in a character. If we take Input in getch( ), it cannot display. If we take Input in getche( ) then it shows the Input character. getchar( ) works similarly and echoes the character that you typed, but require Enter key.

Syntax : char = getch( ); / getche( ); Like………… ch = getch( ); It takes Input and goes in ch.

How to use getch Function

#include <stdio.h>#include <conio.h>main(){

char ch;clrscr();

gotoxy(10,5);printf("Enter Any Key.........");ch=getch();printf("You Press.........%c",ch);

gotoxy(10,10);printf("Enter Another Key.........");ch=getche();printf("You Press.........%c",ch);

gotoxy(10,15);printf("Enter Another Key.........");ch = getchar();gotoxy(40,15);printf("You Press.........%c",ch);getch();

}

Flow Chart symbols:

Start / Stop Input / Output Each specific direction Decision Print

Flow chart uses different shapes for different tasks.1. Each specific direction is in rectangle.2. Each question is in diamond.

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PREPROCESSOR DIRECTIVE:In this if we mention anything will be mentioned above void main: It’s defined as

1) #include 2) #define

#include: #include: necessary to define it above void(main) syntax :- #include <filename.h>

< >is used to find header file in include Directory. But if any include file is found in your own directory or drive then:- syntax:- #include “c:\hello.h”

Note: If include file is found in any specific drive then < > is not used.

MACRO: #define:If we want to define macro then we use #define. If we define #define above main( ) it will be reserve only for that file or for that program.Macro will be define for one line like:

Assignment: Instead of using clrscr( ) function, we want to use cls.We have to create header file name……clear.h and write….

#define cls clrscr()Note : In one time one identifier will be used, we have to use two buffer for two defined macros.

#define cls clrscr()#define go gotoxy(20,5)#define wait printf(“Sadequain”); getch();

How to use defined Macros in our C Program.First we have to include the header file in which the Macro is defined like…….

#include <clear.h>

main(){

clsgowait

}

Macros V/s Function

Macro calls are like function calls but there are some difference. The difference are : In a Macro call the preprocessor replaces the macro template with its macro expansion. Whereas in a Function call the control is passed to a function along with certain arguments, some

calculations are performed in the function and a useful value is returned back from the function.

Usually Macros makes the program to run faster but increase the program size, whereas function make the program smaller and compact.

If we use a macro hundred times in a program, the macro expansion goes to our source code at hundred different places, thus increases the program size. In contrast, if a function is used, then even if it is called

for hundred different places in the program, it only take the same space in a program.

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Function A Prototype declares a function ( It‘ll be terminated) A function call executes a function ( It‘ll be terminated) A function definition is the function itself ( It‘ll not terminated)

Function Declaration ( Prototype ):void sqr( void ); ____________________Note semicolon

What its purpose:

All the variables were defined by name and data type before they were used. The function is declared in a similar way at the beginning of the program before it is called.

The Prototype tells the compiler the name of the function, the data type the function returns ( If any ), and the number and data types of the function’s arguments. _________ void sqr( void ) means …the function returns nothing and takes no arguments: hence two voids.

Prototype is written before the main( ) function.

The key thing to remember about the prototype is that the data type of the return value must agree with that of the declarator in the function definition, and the number of arguments and their data types must agree with those in the function definition.

Calling the Function:

Calling a Function means executing a function. As we use library function like ( printf( ) and scanf( ) ) …..we can also call our own function by simply using its name, including the parentheses following the name. The parentheses let the compiler know that you are referring to a function and not to a variable.

sqr( ); _________________( Ends with semicolon )

(Function Name____Defines function) Function Definition: void sqr(void) _________ (No termination)

Function declarator is not a program statement that’s why it is not terminated. Rather, it tells the compiler that a function is being defined. Function is usually enclosed in braces.

The return statement:The return( ) statement has two purposes. 1. It immediately transfers control from the function back to the calling program.2. And Second, whatever is inside the parenthesis following return is return as a value to the calling program.

Note: return is not necessary written at the end of function, it can occur anywhere in the function.

int add(int a,int b ) ; ____(Prototype) main( ) {

int num1,num2,res; “Actual arguments ” (function call)num1= 5; “Formal arguments ”num2=10;

res = add(num1,num2); int add(int a, int b) {

printf(“Addition = %d”,res); int d; getch(); d = a+b; } return( d );

}

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function name

Header Files and Prototyping:

Header files are used to provide prototypes of library functions. Prototype can provide a mean of avoiding type mismatches b/w actual arguments and formal arguments when a user written function

is called. Header files can give this same protection for library functions.

For example: The prototype for the printf( ) function is stored in the file stdio.h ( along with the prototypes for many other functions ).

User Define Function:

UDF are functions which we define by our self. There are four categories of UDF.

1. Take Nothing return nothing _____void function name(void)2. Take argument return nothing ____void function name(int)3. Take nothing return argument ____int function name(void) 4. Take argument return argument __ int function name(int)

Argument is those values which we pass.

Function known as a group of routine which have specific task to perform. Built in Function are those which are provided by language. User define function are define by user to perform specific task.

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Pointer:

A pointer provides a way of accessing a variable, without referring to the variable directly. The mechanism used for this is the address of the variable.

In order to use a pointer we must define a pointer as like any variable, but pointer variable set aside to store the address.

Defining Pointer variable:

Indicates the pointer Name of pointer variable will point to

integer int *num;

indicates variable is a pointer(i.e... It will hold a address).

General reasons of using pointers. To return more than one value from function. To pass Array and Strings more conveniently from one function to another.

Example of using Pointer: (Calling function by reference)

int sum(int *,int *); // Prototype of sum function.

Takes address of variable

main() Address{

int num1,num2; 1310 5clrscr();

1312 10

printf(“Enter 2 Numbers …….”);scanf(“%d %d”,&num1,&num2);

res = sum(&num1,&num2); Function calling (note arguments 1310 1312 takes address not value)

printf(“Sum of %d and %d = %d”,num1,num2,res);

getch();int sum(int *x,int *y) // Function definition{

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*x = *x + 5;*y = *y + 10;return(*x+*y);

}

int *p;

In both cases, the difference between declaring an integer and a pointer that points to an integer (we'll say "pointer-to-int" from now on) is a single character.

If you declare many pointers on one line in C, you must make sure to put a * by each of the variables. Also, you can put ints next to pointers-to-ints in a declaration by not putting a * next to the int. Confused? Try reading some of the next examples, and see if they help visualize the concepts.

Here are some more examples of declaring pointers:

int *num1, *num2;

char ch, *name;

float *num1, num2;

Notice that you can put both variables and pointers-to-variables on the same line? On the second line, both a character (ch) and a pointer-to-character (name) were both declared. On the third line, a pointer-to-float (num1) and a float (num2 ) were both declared.

Watch Out!

It's easy to see the line

float * num1, num2;and think that you are declaring num1 and num2 both to be of type pointer-to-float. This is NOT the case, however. The * only applies to the variable it's right in front of, in this case num1. By making your *'s touch the front of your variables, you can avoid this mistake. Here's what the improved, easier-to-understand version looks like: float *num1, num2;

However, if you wanted to declare two pointers-to-float, this is what it looks like:

float *num1, *num2;

Notice that they both must have *'s (asteric sign) next to them, so C knows they are pointers.

int *num;

Note: ‘*’ In a definition, it means “pointer data type” just as integer means “integer data type”.*num = *num1 + 5;

Here it means something else: “Value pointed to by”

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