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Computers and Programming CPC
The 1st lecture
Jiří Šebesta
http://www.urel.feec.vutbr.cz/~sebestaj/CPC
• Complete sources are available on the Web pages:
TOPIC
1. Numeric systems
2. Basic structure of the program
3. Algorithms
4. Variables and data in C language
Numeric systems (1/3)
General expression of integer number :
Used systems :
Numeric systems (2/3)
Used symbols are 0 – 9 and letters from alphabet for systems with basis over 10: e.g. for hexadecimal system:
A = 10 B = 11 C = 12 D = 13 E = 14 F = 15
Example for hexadecimal number expression:
Hex. number 0x3CF0 represents decimal value:
3 · 4096 + 12 · 256 + 15 · 16 = 15600
Numeric systems (3/3)
- storage in memory (generally according to standard IEEE754)
mES M
xe
2121 12 1
S is sign bit (+ = 0; - = 1)
E is binary value of exponent
M is binary value of mantissa
General expression of rational (floating point) number:
Basic structure of the program (1/10)
What is a computer program? How to create a computer program?
Assembler = readable machine code using name abbreviations derived from instruction meaning, e.g. MOV, INC, ADD,and their operands (name of register, address in memory, numerical constant…
Basic structure of the program (2/10)
inserted header files (libraries)
#include <math.h> // precompiled header files#include <stdio.h>
int main(void) // header of main function{ // body of main function char c; // variable declaration
printf("ahoj"); // printing fuct. (stdio.h) scanf("%c", &c);// wait until key pressed
(stdio.h) return 0;}
notices
header of main
function
variable declaration
body of function
calling of library
functions command for comeback from function with return value (0)
Basic structure of the program (3/10)
• Application solutions in C:
• CONSOLE APPLICATION (independent on platform) – ANSI C
• APPLICATION DEPENDENT ON PLATFORM (for given OS with utilize offered functions, for given microcontroller with utilize its peripheral) – extensive libraries, e.g. API, MFC, Active X
• Integrated Development Environment IDE
– complete set of tools for application creation including wizards for project setting, e.g. MS Visual Studio
- open source environments, e.g. Code::Blocks or Eclipse or CodeLite (license is not required)
Basic structure of the program (4/10)
• Code::Blocks – our programming tool
• Projectnew project
open a previously
created project
console application = text output in
DOS box
projects for microcontrollers
AVR 8 bitsARM 32 bits
Basic structure of the program (5/10)
• Compiler language setting
Basic structure of the program (6/10)
• Project name setting
Basic structure of the program (7/10)• Kind of compiler setting
GNU – open free softwareGCC = GNU Compiler Collection
Basic structure of the program (8/10)• Debug version vs. release version
DEBUG – excellent debugging, final code is not optimizedRELEASE – final version – optimized code for distribution
Basic structure of the program (9/10)• debugging and executing of an application – menu DEBUG
start of debugging, program stops at
breakpoints
stepping in program including jumps to
functions, by Step out given function can be
early leaved
stepping in program according to the
source code without jumps to functions
breakpoint inserting to given row (where the cursor actually
is placed)
Příklad: Ex01.c
stop of debugging (program can be in
undefined cycle state)
Basic structure of the program (10/10)
• Where you can obtain Code::Blocks ??
Algorithms (1/6)
• Algorithms defines a procedure of operations with data
• Fundamental aspects of algorithm:
Finiteness – algorithm consists of elementary steps (of procedure or process), whereas their number must be finite
Necessatarianism – algorithm must be punctually and clearly defined
Inputs/outputs – algorithm has to defined unambiguous inputs and outputs (data, e.g. given structure of a file)
Effectiveness – algorithm must be effective and optimally used system capability (effectiveness in point of view operation time vs. occupation of operation memory or code length)
Algorithms (2/6)
Versatility – algorithm has to be able to work with required data set in required range
• Basic entities of algorithm:
• Variables
• Start of algorithm
• End of algorithm
• Steps of algorithm
• Subroutines
• Conditions (binary relations)
• Decision making
• Sequences
• Cycles
• Jumps (to use minimally)
Algorithms (3/6)
Resources for algorithm definition (description):
• Lexical – native form: textual (intellectual) guide, order, law – often not too exact definition, then transcription to programming language is impossible
• Graphical – flowchart – transparent visualization of complex algorithms including branching by using defined flowchart symbols with description and oriented flowlines
• Symbolic – algorithm description by exactly defined syntax (key word of programming language; meta-language – generative grammar)
Algorithms (4/6)
Flowchart - symbols:
Algorithm start or algorithm end
Common statement
Conditional branching
Cycle with defined number of repetitions
Cycle with condition in the end
Cycle with condition in the beginning
Manual input (e.g. from keyboard)
Output displaying
File processing
Data saving to a file
Subroutine
Joiner
Oriented flowline
Algorithms (5/6)
• Program that compute roots of any quadratic equation:
ax2 + bx + c = 0
Read coefficients from keyboard. If roots are complex, print error message.
a
acbby
2
42
2,1
Flowchart - example:
Algorithms (6/6)
float a, b, c, y1, y2, r;printf("a = "); scanf("%f", &a);printf("b = "); scanf("%f", &b);printf("c = "); scanf("%f", &c);getchar();
r = b*b-4*a*c;if(r>=0){ y1 = (-b+sqrt(fabs(r)))/(2*a); y2 = (-b-sqrt(fabs(r)))/(2*a); printf("\n 1st root: %.3f", y1); printf("\n 2nd root: %.3f", y2);}else printf("\n Result is not real");
Příklad: Ex02.c
Data and variables (1/15)
• Data – I (Input), – O (Output) , auxiliary (used for internal results)
• Data sources a targets
– file (I/O – binary, text), keyboard (I), console (O), printer (O), communication port (I/O) – e.g. serial port, USB, LPT
- often the functions for programming with data sources and targets are defined as functions for files
• Kind of data (variables) – numerical (integer or rational), characters and strings (string is array of characters terminated by character NULL), arrays (one-dimensional = vectors, multidimensional = matrix, 3D matrix, tensor …), pointer (reference to position in memory), structure (defined encapsulated set of variables with different types)
Data and variables (2/15)• Named place in memory with the desired size (in bytes)• GLOBAL – valid in whole program • LOCAL – valid in body of function (only)
Example: Ex03.c
// precompiled header files#include <stdio.h> // standard inputs and outputsint a = 5; // global variableint main(void) // main function{
int b = 10; // local variablechar c;printf("global: %d\r\n ", a);printf("local: %d\r\n ", b);scanf("%c ", &c);
return 0;}
Data and variables (3/15)
Type Bits Range
unsigned char 8 X <0, +255>
char 8 X <-128, +127>
short int 16 X <-32.768; +32.767>
unsigned int 32 X <0; +4.294.967.295>
int 32 X <-2.147.483.648; +2.147.483.647>
float 32 1,18 10-38 < |X| < 3,40 10+38
double 64 2,23 10-308 < |X| < 1,79 10+308
long double 80 3,37 10-4932 < |X| < 1,18 10+4932
• Types of variables in ANSI C language – numeric types
Data and variables (4/15)
• Numeric types – fixed point for integral numbers
- unsigned number - storing in memory
- signed number - storing in memory
Data and variables (5/15)
• Example unsigned char (8 bits)
• Example signed char (8 bits) – standard expression
Data and variables (6/15)
• Complementary code
• One is subtracted from absolu-te value of coded number and negated
• Example for signed char (8 bits) – complementary coded
• Simpler hardware implementation of ALU
Data and variables (7/15)
• Numerical floating point types
- storage in memory (generally according to IEEE754 standard)
mES M
xe
2121 12 1
S is sign bit
E is binary value in exponent
M is binary value in mantissa
Data and variables (8/15)
• Numerical floating point types
23127
2121M
x ES
521023
2121M
x ES
Float (4 bytes) Double (8 bytes)
Data and variables (9/15)
• Float (4 bytes)
23127
2121M
x ES
Data and variables (10/15)
• Double (8 bytes)
521023
2121M
x ES
Data and variables (11/15)• Types of variables – array
Example: Ex04.c
#include "stdio.h"int main(void){
int A[5] = {0, 1, 2, 3, 4};int B[3][2] = {0, 1, 2, 3, 4, 5};int i,j; char c;for( i=0; i<5; i++)
printf("A[%d] = %d\r\n", i, A[i]);B[0][0] = A[4];for( i=0; i<3; i++){ for( j=0; j<2; j++) printf("B[%d,%d] = %d\r\n", i, j, B[i][j]);}scanf("%c", &c);
return 0;}
Data and variables (12/15)
• String: an array of characters (in memory: 1 byte/character – ASCII coding)
• NTS (Null Terminated Strings) : the last character of string null – spec. notation v C/C++ ’\0’
• Array elements: pointers to characters
Data and variables (13/15)
• String as an array of ASCII codes of characters in memory:
Data and variables (14/15)
• Special characters:\b - backspace BS \f - form feed FF (also clear screen) \n - new line NL
\r - carriage return CR
\t - horizontal tab HT \v - vertical tab (not all versions) \“ - double quotes (not all versions) \' - single quote character '
\\ - backslash character \ \ddd - character ddd, where ddd is an ASCII code given in octal base
\xhhh - character hhh, where hhh is an ASCII code given in hexadecimal base
Data and variables (15/15)
• Types of variables – pointer (= address of variable in memory)
Example: Ex05.c
#include "stdio.h"int main(void){ float x = 3.14, y = 2.27; float* p; // address of float variable
p = &x; // address of x to p *p = y; // content of y on address in p
return 0;}
TOPICS OF THE NEXT LECTURE
1. Expressions
2. Arithmetic conversions
3. Operators
4. Statements if-else and for
THANK YOU FOR YOUR ATTENTION