C Program to Implement Linear Congruential Method for Generating Pseudo Random Number

This is a C Program to generate random numbers using Linear Congruential Generator. The linear congruential generator is a very simple example of a random number generator. All linear congruential generators use this formula:
r_{{n + 1}} = a x r_n + c mod m
Where:
r0 is a seed.
r1, r2, r3, …, are the random numbers.
a, c, m are constants.

Here is source code of the C Program to Implement the linear congruential generator for Pseudo Random Number Generation. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
#include <stdio.h>
```
```
 
```

/* always assuming int is at least 32 bits */

```
int rand();
```
```
int rseed = 0;
```
```
 
```
```
inline void srand(int x) {
```
```
    rseed = x;
```
```
}
```
```
 
```
```
#ifndef MS_RAND
```
```
#define RAND_MAX ((1U << 31) - 1)
```
```
 
```
```
inline int rand() {
```

    return rseed = (rseed * 1103515245 + 12345) & RAND_MAX;

```
}
```
```
 
```
```
#else /* MS rand */
```
```
 
```
```
#define RAND_MAX_32 ((1U << 31) - 1)
```
```
#define RAND_MAX ((1U << 15) - 1)
```
```
 
```
```
inline int rand()
```
```
{
```

    return (rseed = (rseed * 214013 + 2531011) & RAND_MAX_32) >> 16;

```
}
```
```
 
```
```
#endif/* MS_RAND */
```
```
 
```
```
int main() {
```
```
    int i;
```

    printf("rand max is %d\n", RAND_MAX);

```
 
```
```
    for (i = 0; i < 10; i++)
```
```
        printf("%d\n", rand());
```
```
 
```
```
    return 0;
```
```
}
```

Output:

$ gcc LCG.c
$ ./a.out
 
rand max is 2147483647
12345
1406932606
654583775
1449466924
229283573
1109335178
1051550459
1293799192
794471793
551188310

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