C Training Notes

8/2/2019 C Training Notes

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C Programming by

Zulkhairi Mohd Yusof

Rev 1.0


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The following concept will be introduced, examples will be shown and exercises will begiven DIGS (basic), CDR (advanced) and FPASS (professional).

DIGS Declare, Initialize, Get from user and ShowCDR Compute, Decide and RepeatFPASS Function, Pointers, Array, String and Structure

1st concept.Computer as storage area ( memory ).There are three types of storage bin ( data types ).

Int float char

There are three types of data ( constants ).

3.14 255 A(decimal point) (x decimal point) character on keyboardFloat / real integer char

Each type of data can only be stored in its appropriate storage bin.

Program Edit, Save, Compile, Execute using IDE

1st program (skeleton)

void main(void){

}


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Knowing the type of data, and give a name to the storage bin is called declaration.

Data constants : 67, 45, 92, 55, 34 etc (these are exams score)Give it a name ( variable name): ExamScore or Score or Math_Score etc.Data type : integer (because no decimal point!)

We reserve in memory, a place to store exam score of type integer Score

void main( void ){

int Score ; }

Names other than keywords must be declared

ex 1.1

A cashier has currency notes of denominations 10, 50 and 100. If the amount to be withdrawn

is input through the keyboard in hundreds, find the total number of currency notes of eachdenomination the cashier will have to give to the withdrawer.

variable data typeamount eg. 200 integer total10 3 integer total50 0 integer total100 2 integer

void main( void ){

// declare variablesint amount ;int total10, total50, total100 ;

}


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Give an initial value to a variable.

We reserve in memory, a place named Score of type integer, and store aninitial value 35.

Score

void main( void ){

int Score = 35 ; }

ex 2.1

A cashier always has RM250 reserve in the cash register every morning. Find the balance inthe cash register at the end of the day.

void main( void ){

// declare variables

float reserve = 250.0 ;float balance ;}

35


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Sometimes we do not know the value. We get the value from user.We use a library function called scanf .

scanf is not a keyword, therefore it must be declared somewhere. Therefore, either youdeclare the function (chap 3-1) or use a function already declared by somebody else (in thelibrary). To use a library function, we type,

#include < stdio.h > where stdio.h is the library (h is header files)This statement is placed on top of the program (before any function).

eg. to get a data from user into a variable called year, we type:scanf("% d", & year );

%d is a control character. Control characters (preceded by a %) depend on the data type:control character data type%d integer %f float/real%c char

Notice, &year is used instead of year. This is a pointer (chap 3-2).For now, just remember the syntax; scanf("% d", & year );

ex 3.1

Get a radius of a circle from user and compute the area of the circle.

#include < stdio.h >

void main( void ){

// declare variablesfloat radius ;

float area ;

scanf("% f ", & radius );}


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Show the content of the variables to user.

We use a library function called printf .

printf is not a keyword, therefore it must be declared. To use this library function, we type,#include < stdio.h >

eg. to show the content of variable year , we type:printf("% d", year ); -> 2009

The syntax is almost similar to scanf, except for the &.

To show any text on the screen, just type:printf(" hello world "); -> hello world

To print combination of text and variable content on the screen, type:printf(" radius = %f ", radius ); -> radius = 3.146656

ex 4.1

Get a radius of a circle from user. Print and radius on the screen.

#include < stdio.h >

void main( void ){

// declare variablesfloat radius ;float pi = 3.142857 ;

printf("Enter radius : ");scanf("%f", &radius);

printf(" pi = % f \n", pi);printf(" radius = % f ", radius );

}

Now, there is a \n in the syntax. \n is an escape sequence . It can be said as representing aspecial key on your keyboard.escape sequence key\n new line\t horizontal tab\\ backslash


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\b backspace\" quotation mark \' apostrophe


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Common programming mistake:

1. mis-spelled keyword: eg. mian instead of main2. forgot semicolon at the end of statement3. extra semicolon when not needed: eg. void main(void) ;

eg..#include ;4. forgot &: eg. scanf("%d", year);5. missing double quote: eg. printf(hello world);6. misplaced the double quote: eg. printf(radius = %d, radius);

Quiz 1

Get from user his or her initial. Then print a welcome screen.

Heres what the output screen looks like:

Please enter your initial : Z

Assalamualaikum Z!Welcome to C programming.


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5 (C) Compute

An important reason for using a computer very fast calculation.

arithmetic instruction format:var =

Among the arithmetic operators are:+, -, *, /(division), %(mod)Any formula can be translated into the arithmetic instruction format.

eg. area = r 2, translated into: area = pi * radius * radius

Also important is the type conversion . Basically,operation example resultint int 2/5 0int float 2/5.0 0.4float float 2.0/5.0 0.4int int 2%5 2

ex 5.1

Get a radius of a circle from user. Calculate the area of the circle and print the result.

#include

void main(void){

//declare variablesfloat radius;float pi = 3.142857;float area;

printf(Enter radius : );scanf(%f, &radius);

//calculate areaarea = pi * radius * radius;

printf("Area = %f\n", area);}


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Computer can also make decision.We use keywords if , if-else , if-elseif , switch

conditional statement format: where the conditional operators are:>, =, 3.5) printf(The area is ok.);

using switch statement:

eg.switch (ans){

case Y: printf(Yes); break ;case N: printf(No); break ;default: printf(Others);

}

without break, thenif ans==Yes, thecomputer will print

both Yes, No andOthers

No semicolon


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equivalent using if-elseif (ans==Y)

printf(Yes);else{

if (ans==N) printf(No);

else printf(Others);

}

equivalent using if-elseif if (ans==Y)

printf(Yes);elseif (ans==N)

printf(No);else

printf(Others);

eg. 6.1

Decide the fate of Malaysian soccer team based on the number of goals scored against theteam.

#include

void main(void){

int goals ; printf ("Enter the number of goals scored against Malaysia : " );scanf ("%d", &goals );if ( goals


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Computer can continue repeating tasks until instructed to stop.We use keywords for , while and do-while

Basically, need to specify the initial value (init), when to stop (condition) and the step(increment or decrement).

using for statement:

for (initial value; stop condition; step)

Nosemicolon

If using only one statement, usesemicolon.

If more than one statements, useblock. Then, no need semicolon.

indent

eg. for (i=0, i i=0 i=1 i=2

using while statement:

initial value;while (stop condition){

..step;

}

eg. equivalent to the above for statementsi=0;

while (i


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eg. 7.1

Two numbers are entered through the keyboard. Write a program to find the value of onenumber raised to the power of another.

#include

void main(void){

int a, b, result, i ;

printf ("Enter a number : " );scanf ("%d", &a );

printf ("Enter a number (raised to the power of) : " );scanf ("%d", &b );

result = 1;for (i=0; i


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Quiz 2

Write a program to enter five numbers. At the end it should display the count of positive,negative and zeros entered.

Heres what the output screen looks like:

Please enter five numbers:-12 5 0 3 -1

You have 2 positive numbersYou have 2 negative numbersYou have 1 zeros


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Writing functions avoids rewriting the same code over and over. Using functions it becomes easier to write programs and keep track of what they are

doing. If the operation of a program can be divided into separate activities, and eachactivity placed in a different function, then each could be written and checked more or less independently.

Separating the code into modular functions also makes the program easier to designand understand.

Any C program contains at least one function. If a program contains only one function, it must be main( ) . Program execution always

begins with main( ) . There is no limit on the number of functions that might be present in a C program. Each function in a program is called in the sequence specified by the function calls in

main( ) . Function calling - followed by a semicolon

argentina( ) ; Function definition - followed by a pair of braces

void argentina(void ){

statement ;

..statement ;}

A function can call itself. Such a process is called recursion. A function can be called from other function, but a function cannot be defined in

another function. There are basically two types of functions:

Library functions Ex. printf( ) , scanf( ) etc.[compiler comes with a library of standard functions; eg stdio.h, math.h]

User-defined functions Ex. argentina( ) , brazil( ) etc.

General function calling and function definition


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Type 1:accept nothing,return nothing

Type 2:accept something,return nothing

Type 1:accept nothing,return something

Type 1:accept something,return something


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function need to be declared before use (if typed after main ):

void display ( int i ) ;

void main( void )

{int i = 20 ;display ( i ) ;

}void display ( int i ){

int k = 35 ; printf ( "%d\n", i ) ; printf ( "%d\n", k ) ;

}

scope of variable is within function:

void goUK ( int Cathy ){

int k = 35 ; printf ( "%d\n", Cathy ) ; printf ( "%d\n", k ) ;

}void main( void ){

int Khatijah = 20 ;goUK (Khatijah ) ;

}

example of call by values :

void display ( int i ) ;

void main( void ){

int i = 20 ;

display ( i ) ; printf ( In main i = %d\n", i ) ;}void display ( int i ){

i = i + 1 ; printf ( In display i = %d\n", i ) ;

}


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- when we have the same data type , and we want to combine them

example on array:

//This program demonstrate the usual//DIS - Declare, Initialize and Show

#include

void main (void){

//declare variablesint num1, num2, num3float Avg;

//initializenum1 = 1; num2 = 2; num3 = 4;

Avg = (num1 + num2 + num3) / 3.0;

printf ("The numbers are :\n"); printf ("%d\n", num1);

printf ("%d\n", num2); printf ("%d\n", num3);

printf ("Average = %.2f\n", Avg);}

//This program demonstrate the use of array//DIS - Declare, Initialize and Show

#include

void main (void){

//declare arrayint num[3]; //num[0], num[1], and num[2]float Avg;

//initialize arraynum[0] = 1; num[1] = 2; num[2] = 4;

Avg = (num[0] + num[1] + num[2]) / 3.0;

printf ("The numbers are :\n"); printf ("%d\n", num[0]);

printf ("%d\n", num[1]); printf ("%d\n", num[2]);



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//This program demonstrate the use of array//DGS - Declare, Get (from user) and Show

#include

void main (void){

int num[3];

float Avg;

printf ("Enter 3 numbers : ");scanf ("%d", &num[0]);scanf ("%d", &num[1]);scanf ("%d", &num[2]);

Avg = (num[0] + num[1] + num[2]) / 3.0;

printf ("The numbers are :\n"); printf ("%d\n", num[0]); printf ("%d\n", num[1]); printf ("%d\n", num[2]);


//This program demonstrate the use of array//Use 'for' loop and 'define'

#include #define no 3

void main (void){

int num[no];

int i, Sum;float Avg;

//get input from user printf ("Enter %d numbers : ", no);for (i=0; i


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- when we have the same data type (char) , and we want to combine them

example on string:

#include

void main (void){

char name[5] = {'A','h','m','a','d'};int i;

for (i=0;i


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#include

void main (void){

char name[5];int i, pos=0;

printf("Enter your name : ");gets(name);

printf("\nYour name is : "); puts(name);

for (i=0;i


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- when we have different data types , and we want to combine them

look at this function later!

void getAvgMath (struct score *student, float *Avg){

int i, Sum;

for (Sum=0, i=0; i


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example of program using structure:

#include struct score

{ char name[10];int Math;int Science;int English;

};

void main (void){

int i;int Max, Min;

float Avg;struct score student[4] = {

"Amin", 55, 61, 86,"Aman", 48, 69, 76,"Azim", 88, 91, 77,"Azam", 78, 71, 56,

};

/* //get input from user for (i=0; i


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Quiz 3

Create a structure to specify data of customers in a bank. The data should include;Account No, Name, Balance, Year Join

Use the following information for your program:Account No Name Balance Year JoinC011 Dahlia bt Atan 200 2004D012 Abu bin Bakar 20 2005B013 Ramli bin Amin 145 2003D014 Fatimah bt Haris 35 2005D017 Wong Hong Kau 45 2005

Write a function to print the Account number and name of each customer with balance below RM 50

Example Output :

** Welcome to Bank of Wopuchitau **

** This utility lets you to list all customers with balance below certain value.

** Please enter the cutoff value: RM 50

The customers with balance below RM 50:1. D012 Abu bin Bakar 202. D014 Fatimah bt Haris 353. D017 Wong Hong Kau 45

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