#include <stdlib.h> header file must be included for following function.
max(), min() : max returns the larger of two values and min returns the smaller of two values. max and min are macros that generate inline code to find the maximum or minimum value of two values.
Declaration:
(type) max(a, b);
(type) min(a, b);
/* Example of max/min */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
void main()
{
int x,y,z;
printf("\nEnter two Numbers : ");
scanf("%d%d",&x,&y);
clrscr();
z = max(x, y);
printf("The larger between %d and %d is %d\n", x,y,z);
z=min(x,y);
printf("The smaller between %d and %d is %d\n", x,y,z);
getch();
}
Output :
The larger between 12 and 56 is 56
The smaller between 12 and 56 is 12
random() : random returns a random number between 0 and (num-1).
rand() : is a multiplicative congruential random number generator.
randomize () : randomize initializes the random number generator with a random value. Because randomize is implemented as a macro that calls the time function prototyped in TIME.H, you should include TIME.H. Unless you use randomize(), you will get same value keep retuning by random() function.
/* Example of rand() / random() / randomize() */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
#include <time.h>
/* prints a random number in the range 0 to 55 */
void main()
{
randomize();
clrscr();
printf("Random number in the 0-55 range: %d\n", random (56));
getch();
}
Output :
Random number in the 0-55 range: 17
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
#include <time.h>
void main()
{
int i;
randomize();
clrscr();
printf("Five random numbers from 0 to 55\n\n");
for(i=0; i<5; i++)
printf("%d\n", rand() % 56);
getch();
}
Output :
Five random numbers from 0 to 55
19
36
53
18
31
atof() : atof converts a string to a floating point. In atof, the first unrecognized character ends the conversion. atold converts a string to a long double.
/* Exmaple of atof() */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
void main()
{
float num;
char *str = "8945.95";
clrscr();
num = atof(str);
printf("String = %s Converted to float = %8.2f\n", str,num);
getch();
}
Output :
String = 8945.95 Converted to float = 8945.95
atoll() : Converts a string to a long
/* Example of atol() */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
void main()
{
long num;
char *lstr = "98765432";
clrscr();
num = atol(lstr);
printf("string = %s integer = %ld\n", lstr, num);
getch();
}
Output :
string = 98765432 integer = 98765432
itoa() : itoa converts an integer to a string. itoa, ltoa, and ultoa convert value to a null-terminated string and store the result in string. If radix is 10 then conversion will be in decimal numbers and you can use 2, 8, 16 for conversion to binary, octal or in Hexa.
/* Example of itoa() */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
void main()
{
int number = 75;
char string[25];
clrscr();
itoa(number, string, 10);
printf("integer = %d string(Decimal) = %s\n", number, string);
itoa(number, string, 2);
printf("integer = %d string(Binary) = %s\n", number, string);
itoa(number, string, 8);
printf("integer = %d string(Octal) = %s\n", number, string);
itoa(number, string, 16);
printf("integer = %d string(Hexadecimal) = %s\n", number, string);
getch();
}
Output :
integer = 75 string(Decimal) = 75
integer = 75 string(Binary) = 1001011
integer = 75 string(Octal) = 113
integer = 75 string(Hexadecimal) = 4b
div : divides two integers and returns both the quotient and the remainder, ldiv divides two longs
Declaration:
div_t div(int numer, int denom);
/* Example of div) */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
div_t x;
void main()
{
x = div(10,3);
clrscr();
printf("10 div 3 = %d remainder %d\n",
x.quot, x.rem);
getch();
}
Output :
10 div 3 = 3 remainder 1
free() : free deallocates a memory block allocated by a previous call to calloc, use farfree to release a large block of memory. Tiny model program can't use farfree.
/* Example of free) */
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
void main()
{
char *str;
str = (char *) malloc(20); // allocate memory to string
clrscr();
printf("\nEnter a string upto 20 characters : ");
gets(str);
printf("\nString is %s\n", str);
free(str);
getch();
return 0;
}
Output;
Enter a string upto 20 characters : Freezing Memory
String is Freezing Memory
Following functions are part of #include <process.h>, used to execute certain system commands.
system() : Issues a DOS command. system invokes the DOS command interpreter file from inside an executing C program to execute a DOS command, batch file, or other program. To execute these programs, you have to run it directly from DOS prompt by executing your .EXE files.
/* Example of free) */
#include <process.h>
#include <conio.h>
#include <stdio.h>
void main()
{
clrscr();
printf("Run a DOS command, show the current directory list\n");
system("dir");
getch();
}
Output :
Run a DOS command, show the current directory list
Volume in drive D is Application
Volume Serial Number is C88E-DBD1
Directory of D:\
A C 153 07/03/11 1:41p
A TXT 4394 06/05/11 8:48a
M TXT 41166 06/19/11 10:28a
M1 TXT 22754 06/19/11 3:46p
PROGRA~1 <dir> 06/22/08 7:53p SS TXT 5828 05/22/11 2:28p
T C 175 07/03/11 3:07p
X TXT 1016 05/22/11 2:12p
8 file(s) 75486 bytes
1023932928 bytes freeabort() : Abnormally terminates a process, abort writes a termination message on stderr ("Abnormal program termination")
/* Example of abort() */
#include <process.h>
#include <conio.h>
#include <stdio.h>
void main()
{
clrscr();
printf("\Aborting\n\n ");
abort();
printf("Never reached statement");
getch();
}
Output :
Aborting
Abnormal program termination
exit() : terminates the program. exit terminates the calling process. Before termination, exit does the
/* Example of exit() */
#include <process.h>
#include <conio.h>
#include <stdio.h>
void main()
{
int a,b,c;
clrscr();
printf("Enter two no. : ");
scanf("%d%d",&a,&b);
c=a+b;
printf("\n%d + %d = %d",a,b,c);
exit(0);
//Exit program and following statements are unreachable
c=a*b;
printf("\n%d * %d = %d",a,b,c);
getch();
}
Output :
Enter two no. : 55
67
55 + 67 = 122
Next week it will be functions that can run DOS commands and the functions that gives you system date and times.
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