Computers and Programming CPC

The 1 lecture

Jiří Šebesta Sumber dari : www.urel.feec.vutbr.cz/~sebestaj/CPC/LE01.ppt

Complete sources are available on the Web pages:

1. Numeric systems

2. Basic structure of the program

3. Algorithms

4. Variables and data in C language General expression of integer number : Used systems :

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

storage in memory (generally according to standard IEEE754)

       

      ^{ } ^ _m ^{E S}

M x ^e

1 ¹ ² 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:

How to create a computer What is a computer program? 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, inserted header files (libraries) notices header of

#include <math.h> // precompiled header files

main

#include <stdio.h>

function

int main( void ) // header of main function

body of

{ // body of main function

function

char c; // variable declaration

variable

printf( "ahoj" ); // printing fuct. (stdio.h)

declaration

scanf( "%c" , &c );// wait until key pressed (stdio.h) return 0;

calling of

}

library functions command for comeback from

Application solutions i
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)

Code::Blocks – our programming tool

new project open a previously created project

Project

console application = text output in

projects for microcontrollers AVR 8 bits

ARM 32 bits

Compiler language setting
Project name setting

Kind of compiler setting

GNU – open free software

Debug version vs. release version

DEBUG – excellent debugging, final code is not optimized

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 stepping in program according to the source code without jumps to functions breakpoint inserting to given row (where the cursor actually is placed) stop of debugging

(program can be in undefined cycle state)

Where you can obtain Code::Blocks ??
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

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

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-
Flowchart - symbols: Algorithm start or Manual input (e.g. algorithm end from keyboard) Output displaying Common statement File processing Conditional branching Data saving to a file Cycle with defined number of repetitions Subroutine Cycle with condition Joiner in the end Cycle with condition Oriented flowline in the beginning
Flowchart - example:
• Program that compute roots of
any quadratic equation:
2
ax + bx + c =
Read coefficients from
keyboard. If roots are complex,
print error message.
2 b b 4 ac
   y
 1 ,
2
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" );
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

Named place in memory with the desired size (in bytes)

GLOBAL
– valid in whole program
LOCAL – valid in body of function (only)
// precompiled header files #include <stdio.h> // standard inputs and outputs int a = 5; // global variable int main( void ) // main function { int b = 10; // local variable char c; printf( "global: %d\r\n " , a); printf( "local: %d\r\n " , b); scanf( "%c " , &c); return 0; }
Types of variables in ANSI C language
– numeric types
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

• Numeric types – fixed point for integral numbers
unsigned number - storing in memory

signed number - storing in memory
Example
(8 bits) unsigned char
Example
(8 bits) – standard expression signed char
Complementary code
Example for
signed (8 bits) – char
One is subtracted from absolu-
complementary coded te value of coded number and negated
Simpler hardware

Numerical floating point types
storage in memory (generally according to IEEE754 standard)
       
      ^{ } ^ _m ^{E S}
M x ^e
2
1
2
1 ¹ ² ¹ S is sign bit E is binary value in exponent M is binary value in mantissa
Numerical floating point types
   
      ^ ₂₃ ¹²⁷
2
1
2
x ^{E S}  
   
    ^ ₅₂ ¹⁰²³
2
1
2
1 M x ^{E S}
Float (4 bytes) Double (8 bytes)
Float (4 bytes)
     
      ^ ₂₃ ¹²⁷
2
1
2
1 M x ^{E S}
Double (8 bytes)
     
      ^ ₅₂ ¹⁰²³
2
1
2
1 M x ^{E S}
Types of variables
– array
#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; }
String: an array of characters
(in memory: 1 byte/character – ASCII coding) (Null Terminated Strings) : the last character of
NTS
string null – spec. notation v C/C++ ’\0’
Array elements: pointers to characters

• String as an array of ASCII codes of characters in
memory:
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
Types of variables
– pointer (= address of variable in memory)
#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; }
1. Expressions
2. Arithmetic conversions
3. Operators
4. Statements if-else and for THANK YOU FOR YOUR ATTENTION

Computers and Programming CPC