C workshop Yuli Kaplunovsky - yuli@magniel Today - Introduction to C

C workshopYuli Kaplunovsky - yuli@magniel.comToday - Introduction to C Recommended book: The C programming Language / Kernighan & Ritchie

My first program #include <stdio.h> void main() { printf("Hello World!\n"); } Output: Hello World!

C structure • Function oriented (‘goto’ is not recommended) • First function is always called main • Contains many libraries (e.g. stdio.h, stdlib.h, math.h) with many predefined functions. • CaSe SeNsItIvE (e.g. ‘Main’ instead of ‘main’ won’t work) • ALWAYS USE: • Indentation • Meaningful names for functions and variables • Plenty of remarks

Variables • int – an integer number maximum value is 2,147,483,647 (or 2^31) minimum value is -2,147,483,648 • double – real number, represented as floating point (64 bits long) • char – represents a single character

Variables sample #1 #include <stdio.h> void main() { int I,J,K; I = 10; J = 20; K = I + J; printf("K is %d\n", K); } Output: K is 30

Variable sample #2 #include <stdio.h> void main() { double X,Y,Z; X = 10.0; Y = 20.0; Z = X / Y; printf("Z is %g\n", Z); } Output: Z is 0.5

while #include <stdio.h> /* Print Fahrenheit-Celsius table for fahr = 0, 20, .., 300 */ void main() { int fahr, celsius; int lower, upper, step; lower = 0; /* lower limit of temerature table */ upper = 300; /* upper limit */ step = 20; /* step size */ fahr = lower; while ( fahr <= upper ) { celsius = 5 * (fahr - 32) / 9; printf("%d\t%d\n", fahr, celsius ); fahr = fahr + step; } } Output: 0 -17 20 -6 40 4 60 15 80 26 100 37 120 48 140 60 160 71 180 82 200 93 220 104 240 115 260 126 280 137 300 148

for • Syntax: for ( initialization ; condition ; do ) { block } #include <stdio.h> void main() { int I; printf("I = "); for ( I = 0 ; I < 10 ; I++ ) printf("%d, ", I ); printf("\n"); } Output: I = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,

for - another example Output: 0 -17.7778 20 -6.66667 40 4.44444 60 15.5556 80 26.6667 100 37.7778 120 48.8889 140 60 160 71.1111 180 82.2222 200 93.3333 220 104.444 240 115.556 260 126.667 280 137.778 300 148.889 #include <stdio.h> void main() { int fahr; for ( fahr = 0 ; fahr <= 300 ; fahr = fahr + 20 ) printf("%d %g\n", fahr, (5.0 / 9.0) * (fahr - 32) ); }

if • if ( condition ) { block #1 } else { block #2 } (optional) • Example:if ( Y > X ) Z = X;else Z = Y; • For comparisons use: > < <= >= == • Important remark: a block should be surrounded with {} if it contains more than one command.

If - multiple conditions • if ( (condition1 || condition2 ) && condition3) ... • Examples:if ( Y > X && Y > Z ) Z = X;int bTerminate; if ( I == 10 || bTerminate ) break; • break is used to get out of for & while loops • condition2 is FALSE when bTerminate is 0 and is TRUE when bTerminate is NOT 0

Functions • Return-value function-name( parameters ) { … returnvalue; } • Calling the function:I = function-name( 10, 20 );

Function example #include <stdio.h> int Add2( int A, int B ) { int C; C = A + B; return C; } void main() { int I; I = Add2( 10, 20 ); printf("Add2 function returns = %d\n", I); } Output: Add2 function returns = 30

Arrays • ALWAYS start from 0Last item is N-1 • Example:int Ar[10];Ar[0] = 22;Ar[9] = Ar[0] + 22;I = 4; Ar[I] = Ar[I+1];

#include <stdio.h> // Guess what this program does... void main() { double X[10] = { 2, 4.2, 11.2, 3, 99.2, -23.2, 33, 11, 43, 9 }; double Y; int I, J; for ( I = 0 ; I < 9 ; I++ ) { for ( J = I+1 ; J < 10 ; J++ ) { if ( X[I] > X[J] ) { // Switch variables in array Y = X[I]; X[I] = X[J]; X[J] = Y; } } } // print results for ( I = 0 ; I < 10 ; I++ ) printf("%g, ", X[I]); } Output: -23.2, 2, 3, 4.2, 9, 11, 11.2, 33, 43, 99.2,

C workshop Yuli Kaplunovsky - yuli@magniel Today - Introduction to C