C workshop #3
flow control / strings
1
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");
Output:
*
**
***
****
0, 1, 2, 3,
1, 2, 3, 4,
1, 2, 3,
I = 0;
while ( I++ < 4 )
printf("%d, ",I);
printf("\n");
}
I = 0;
while ( ++I < 4 )
printf("%d, ",I);
printf("\n");
2
goto
• Continue executing at different location
#include <stdio.h>
void main()
{
printf("1\n");
goto LABEL_QQ;
printf("2\n");
Output:
1
3
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.
3
switch / case
#include <stdio.h>
void main()
{
int I;
for ( I = 0 ; I < 10 ; I++ ) {
switch (I) {
Output:
**How are you???**
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");
}
4
continue
• Used in ‘for / while / do’ loops
#include <stdio.h>
void main()
{
Output:
0* 1* 2* 3* 4 5* 6* 7 8* 9*
int I;
for ( I = 0 ; I < 10 ; I++ ) {
printf(“ %d", I );
if ( I == 9 || I==3 ) continue;
printf(“*");
}
printf("\n");
}
5
break
• Used in ‘for / while / do’ loops
#include <stdio.h>
void main()
{
Output:
0* 1* 2* 3* 4
int I;
for ( I = 0 ; I < 10 ; I++ ) {
printf(“ %d", I );
if ( I == 4 )
break;
printf(“*");
}
printf("\n");
}
6
characters
• A single byte (a bytes defined as a number
between 0 to 255), represents a single character
Sample 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=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=~
7
char sample #1
#include <stdio.h>
void main()
{
char C, G, L;
C = 't';
printf("%c\n", C );
C = 't' + 1;
Output:
t
u
uu
Now, dear user, press any key, and then press ENTER
3
You entered: 3
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 );
}
8
char sample #2
#include <stdio.h>
void main()
{
char C;
for ( C = 32 ; C < 127 ; C++ ) {
printf("%3d=%c
}
printf("\n");
}
", C, C );
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=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=~
9
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’).
Output:
#include <stdio.h>
void main()
{
char S[100];
Hi!
Hi!
72 105 33 0
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] );
}
10
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 );
Output:
Good Morning!
Test0123
s
strcpy( ST, "Test0123" );
printf("%s\n", ST );
C = ST[2];
printf("%c\n", C );
}
11
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
12
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
13
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++;
Output:
}
}
Good Morning 123!!
GOOD MORNING 123!!
void main()
{
char ST[100];
strcpy( ST, "Good Morning 123!!\n" );
printf( ST );
ToCap( ST );
printf( ST );
}
14
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++;
}
}
Output:
Good Morning 123!!
GOOD MORNING 123!!
void main()
{
char ST[100];
strcpy( ST, "Good Morning 123!!\n" );
printf( ST );
ToCap( ST );
printf( ST );
}
15
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
16
sample #7 (float type)
#include <stdio.h>
void main()
{
int J;
float F;
double D;
printf("Please enter a number\n");
scanf("%d", &J );
Output:
Please enter a number
10
Please enter a fractional number
33.44
Your numbers are: 10 33.44 33.44
printf("Please enter a fractional number\n");
scanf("%f", &F );
D = F;
printf("Your numbers are: %d %g %g\n", J, F, D );
}
17
strings sample #8 (sprintf)
#include <stdio.h>
#include <string.h>
void main()
{
char ST[250];
int I = 22;
sprintf( ST, "Test123 %d", I );
Output:
Test123 22
printf( "%s\n", ST );
}
18
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!!!'
19
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],
int N = 2, I, J;
for ( I = 0 ; I <
for ( J = 0 ;
X[I][J] =
Y[10][10], Z[10][10];
N ; I++ )
J < N ; 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");
printf("\nMatrix Y is: \n");
printf("\nMatrix Z is: \n");
PrintMat( N, X );
PrintMat( N, Y );
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,
20
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.
21
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
22