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C workshop #3

flow control / strings

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do / while / for#include <stdio.h>

void main(){

int I = 1, J;do {for ( J = 0 ; J < I ; J++ ) printf("*");printf("\n");I++;} while ( I < 5 );

I = 0;do { printf("%d, ",I);I++;} while ( I < 4 );printf("\n");

I = 0;while ( I++ < 4 )printf("%d, ",I);printf("\n");

I = 0;while ( ++I < 4 )printf("%d, ",I);printf("\n");

}

Output:**********0, 1, 2, 3,1, 2, 3, 4,1, 2, 3,

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goto• Continue executing at different location#include <stdio.h>void main(){

printf("1\n");goto LABEL_QQ;

printf("2\n");

LABEL_QQ:printf("3\n");

}

• The label can be anything, e.g. Cont_here, Line123, AfterTest.• Cannot jump into a block, or into a different function.• NOT RECOMMENDED TO USE. Used mainly with error handling.

Output:13

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switch / case#include <stdio.h>void main(){ int I; for ( I = 0 ; I < 10 ; I++ ) { switch (I) {

case 2: printf("How "); break; case 3: printf("are "); break; case 4: printf("you"); break; case 5: case 6: case 7: printf("?"); break; default: printf("*"); } }

printf("\n");}

Output:**How are you???**

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continue• Used in ‘for / while / do’ loops #include <stdio.h>void main(){ int I; for ( I = 0 ; I < 10 ; I++ ) { printf(“ %d", I ); if ( I == 9 || I==3 ) continue; printf(“*"); } printf("\n");}

Output: 0* 1* 2* 3* 4 5* 6* 7 8* 9*

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break• Used in ‘for / while / do’ loops #include <stdio.h>void main(){ int I; for ( I = 0 ; I < 10 ; I++ ) { printf(“ %d", I ); if ( I == 4 ) break; printf(“*"); } printf("\n");}

Output: 0* 1* 2* 3* 4

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characters• A single byte (a bytes defined as a number

between 0 to 255), represents a single characterSample of character representations: 32= 33=! 34=" 35=# 36=$ 37=% 38=& 39=' 40=( 41=) 42=* 43=+ 44=, 45=- 46=. 47=/ 48=0 49=1 50=2 51=3 52=4 53=5 54=6 55=7 56=8 57=9 58=: 59=; 60=< 61== 62=> 63=? 64=@ 65=A 66=B 67=C 68=D 69=E 70=F 71=G 72=H 73=I 74=J 75=K 76=L 77=M 78=N 79=O 80=P 81=Q 82=R 83=S 84=T 85=U 86=V 87=W 88=X 89=Y 90=Z 91=[ 92=\ 93=] 94=^ 95=_ 96=` 97=a 98=b 99=c 100=d 101=e102=f 103=g 104=h 105=i 106=j 107=k 108=l 109=m 110=n 111=o112=p 113=q 114=r 115=s 116=t 117=u 118=v 119=w 120=x 121=y122=z 123={ 124=| 125=} 126=~

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char sample #1#include <stdio.h>void main(){ char C, G, L;

C = 't'; printf("%c\n", C );

C = 't' + 1; printf("%c\n", C );

G = C; printf("%c %c\n", G, C );

printf("Now, dear user, press any key, and then press ENTER\n"); L = getchar(); printf("You entered: %c\n", L );}

Output:tuu uNow, dear user, press any key, and then press ENTER3You entered: 3

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char sample #2#include <stdio.h>void main(){ char C; for ( C = 32 ; C < 127 ; C++ ) { printf("%3d=%c ", C, C ); } printf("\n");}

Output: 32= 33=! 34=" 35=# 36=$ 37=% 38=& 39=' 40=( 41=) 42=* 43=+ 44=, 45=- 46=. 47=/ 48=0 49=1 50=2 51=3 52=4 53=5 54=6 55=7 56=8 57=9 58=: 59=; 60=< 61== 62=> 63=? 64=@ 65=A 66=B 67=C 68=D 69=E 70=F 71=G 72=H 73=I 74=J 75=K 76=L 77=M 78=N 79=O 80=P 81=Q 82=R 83=S 84=T 85=U 86=V 87=W 88=X 89=Y 90=Z 91=[ 92=\ 93=] 94=^ 95=_ 96=` 97=a 98=b 99=c 100=d 101=e102=f 103=g 104=h 105=i 106=j 107=k 108=l 109=m 110=n 111=o112=p 113=q 114=r 115=s 116=t 117=u 118=v 119=w 120=x 121=y122=z 123={ 124=| 125=} 126=~

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strings• string is an array of characters• To have meaningful data, the last character of the

string has to be \0 (not to confuse with the character ‘0’).

#include <stdio.h>void main(){ char S[100]; S[0] = 'H'; S[1] = 'i'; S[2] = '!'; S[3] = '\0'; printf("%s\n", S ); printf("%c %c %c %ce\n", S[0], S[1], S[2], S[3] ); printf("%d %d %d %d\n", S[0], S[1], S[2], S[3] );}

Output:Hi!H i !72 105 33 0

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strings sample #2#include <stdio.h>#include <string.h>void main(){ char ST[100]; char ST2[] = "Good Morning!"; char C;

strcpy( ST, ST2 ); printf("%s\n", ST );

strcpy( ST, "Test0123" ); printf("%s\n", ST );

C = ST[2]; printf("%c\n", C );}

Output:Good Morning!Test0123s

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strings sample #3#include <stdio.h>#include <string.h>void main(){ char ST[100]; int I = 33; strcpy( ST, "%d\n" ); printf( ST, I );}

Output:33

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strings sample #4 (strcat, strlen, strstr)#include <stdio.h>#include <string.h>void main(){ char ST[100]; char *P; int L; strcpy( ST, "Beginning " ); strcat( ST, "End"); L = strlen( ST ); P = strstr( ST, "nni" ); if ( P != NULL ) *P = 'N'; printf( "%s, %d\n", ST, L );}

Output:BegiNning End, 13

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strings sample #5#include <stdio.h>#include <string.h>

void ToCap( char *ST ){ while ( *ST != 0 ) { if ( *ST >= 'a' && *ST <='z' ) *ST = (*ST - 'a') + 'A'; ST++; }}

void main(){ char ST[100]; strcpy( ST, "Good Morning 123!!\n" ); printf( ST );

ToCap( ST ); printf( ST );}

Output:Good Morning 123!!GOOD MORNING 123!!

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strings sample #5.5 (SAME)#include <stdio.h>#include <string.h>

void ToCap( char *P ){ while ( *P != 0 ) { if ( *P >= 'a' && *P <='z' ) *P = (*P - 'a') + 'A'; P++; }}

void main(){ char ST[100]; strcpy( ST, "Good Morning 123!!\n" ); printf( ST );

ToCap( ST ); printf( ST );}

Output:Good Morning 123!!GOOD MORNING 123!!

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strings sample #6 (scanf)#include <stdio.h>#include <string.h>

void main(){ char ST[100]; printf("Please enter a word\n"); scanf("%s", ST ); printf("Your word is: \"%s\“,\nand it has %d characters\n", ST, strlen(ST) );}

Output:Please enter a wordHello!!!Your word is: "Hello!!!", and it has 8 characters

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sample #7 (float type)#include <stdio.h>

void main(){ int J; float F; double D;

printf("Please enter a number\n"); scanf("%d", &J );

printf("Please enter a fractional number\n"); scanf("%f", &F ); D = F;

printf("Your numbers are: %d %g %g\n", J, F, D );}

Output:Please enter a number10Please enter a fractional number33.44Your numbers are: 10 33.44 33.44

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strings sample #8 (sprintf)#include <stdio.h>#include <string.h>

void main(){ char ST[250]; int I = 22; sprintf( ST, "Test123 %d", I );

printf( "%s\n", ST );}

Output:Test123 22

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strings sample #9 (gets)#include <stdio.h>#include <string.h>

void main(){ char ST[250]; printf("Enter a word\n"); gets( ST ); printf("You entered: '%s'\n", ST );}

Output:Enter a wordToo many examples!!!You entered: 'Too many examples!!!'

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Matrix multiplication example#include <stdio.h>#include <stdlib.h>void MatMult( int N, double A[10][10], double B[10][10], double C[10][10] ){ int I,J,K; double D; for ( I = 0 ; I < N ; I++ ) { for ( J = 0 ; J < N ; J++ ) { D = 0.0; for ( K = 0 ; K < N ; K++ ) D = D + A[I][K] * B[K][J]; C[I][J] = D; } }}void PrintMat( int N, double A[10][10] ){ int I,J; for ( I = 0 ; I < N ; I++ ) { for ( J = 0 ; J < N ; J++ ) printf("%g, ", A[I][J] ); printf("\n"); }}void main(){ double X[10][10], Y[10][10], Z[10][10]; int N = 2, I, J; for ( I = 0 ; I < N ; I++ ) for ( J = 0 ; J < N ; J++ ) X[I][J] = rand() % 10; for ( I = 0 ; I < N ; I++ ) for ( J = 0 ; J < N ; J++ ) Y[I][J] = rand() % 10;

MatMult( N, X, Y, Z ); printf("Matrix X is: \n"); PrintMat( N, X ); printf("\nMatrix Y is: \n"); PrintMat( N, Y ); printf("\nMatrix Z is: \n"); PrintMat( N, Z );}

Output:Matrix X is:1, 7,4, 0,

Matrix Y is:9, 4,8, 8,

Matrix Z is:65, 60,36, 16,

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Quiz (15 minutes)1. Write a program that prints the multiplication table

2. Write a FUNCTION that gets as an input two strings, compares them, and returns either 0 or 1. If the strings are the same it returns 1, if not, it returns 0.

Write a program that has two hard-coded (predefined) strings and uses the above function.

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Next• Wednesday

More standard libraries (math.h, stdlib.h, etc.)How to create a library of our own functionsMore pointers (type casting)The “Numerical Recipes” package Financial applications

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