1. C workshop #3
flow control / strings

2. do / while / for Output: * ** *** **** 0, 1, 2, 3, 1, 2, 3, 4,
#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;
printf("%d, ",I);
} while ( I < 4 );
while ( I++ < 4 )
while ( ++I < 4 ) }
Output: * **
***
****
0, 1, 2, 3,
1, 2, 3, 4,
1, 2, 3,

3. goto Continue executing at different location Output:
#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: 1 3

4. switch / case Output: **How are you???** #include <stdio.h>
void main() {
int I;
for ( I = 0 ; I < 10 ; I++ ) {
switch (I) {
case 2:
printf("How ");
break;
case 3:
printf("are ");
case 4:
printf("you");
case 5:
case 6:
case 7:
printf("?");
default:
printf("*"); }
printf("\n");
Output:
**How are you???**

5. continue Used in ‘for / while / do’ loops Output:
#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*

6. break Used in ‘for / while / do’ loops Output: 0* 1* 2* 3* 4
#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

7. characters
A single byte (a bytes defined as a number between 0 to 255), represents a single character
Sample of character representations:
32= =! 34=" 35=# 36=$ 37=% 38=& 39=' 40=( 41=)
42=* 43= =, 45= = =/ 48= = = =3
52= = = = = = =: 59=; 60=< 61==
62=> 63=? 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=e
102=f 103=g 104=h 105=i 106=j 107=k 108=l 109=m 110=n 111=o
112=p 113=q 114=r 115=s 116=t 117=u 118=v 119=w 120=x 121=y
122=z 123={ 124=| 125=} 126=~

8. char sample #1 Output: t u u u
#include <stdio.h>
void main() {
char C, G, L;
C = 't';
printf("%c\n", C );
C = 't' + 1;
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: t u
u u
Now, dear user, press any key, and then press ENTER 3
You entered: 3

9. 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= =! 34=" 35=# 36=$ 37=% 38=& 39=' 40=( 41=)
42=* 43= =, 45= = =/ 48= = = =3
52= = = = = = =: 59=; 60=< 61==
62=> 63=? 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=e
102=f 103=g 104=h 105=i 106=j 107=k 108=l 109=m 110=n 111=o
112=p 113=q 114=r 115=s 116=t 117=u 118=v 119=w 120=x 121=y
122=z 123={ 124=| 125=} 126=~

10. 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 !

11. strings sample #2 Output: Good Morning! Test0123 s
#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" );
C = ST[2];
printf("%c\n", C ); }
Output:
Good Morning!
Test0123 s

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

13. 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

14. strings sample #5 Output: Good Morning 123!! GOOD MORNING 123!!
#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 );
Output:
Good Morning 123!!
GOOD MORNING 123!!

15. 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 );
Output:
Good Morning 123!!
GOOD MORNING 123!!

16. 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 word
Hello!!!
Your word is: "Hello!!!",
and it has 8 characters

17. sample #7 (float type) Output: Please enter a number 10
#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 number 10
Please enter a fractional number
33.44
Your numbers are:

18. 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

19. 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 word
Too many examples!!!
You entered: 'Too many examples!!!'

20. 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 ( 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++ )
X[I][J] = rand() % 10;
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,

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

22. Next
Wednesday More standard libraries (math.h, stdlib.h, etc.) How to create a library of our own functions More pointers (type casting) The “Numerical Recipes” package Financial applications
Saturday C/C++ Interface to excel Question session