1. ECE 103 Engineering Programming Chapter 51 Random Numbers
Herbert G. Mayer, PSU CS
Status 6/4/2014
Initial content copied verbatim from
ECE 103 material developed by
Professor Phillip PSU ECE

2. Syllabus
srand()
sand()

3. Random Number Generator
C has library functions to input and output strings.
Use #include <stdio.h>
In the following table, char * is a pointer to a character array that contains a string.
RNG Functions
void srand (unsigned int seed)
Initializes the RNG with a seed value
int rand (void)
Returns a pseudo-random integral number 2

4. String I/O Functions
C has library functions to input and output strings.
Use #include <stdio.h>
In the following table, char * is a pointer to a character array that contains a string.
int printf (const char * fmt, …)
Prints formatted output to console
int sprintf (char * s, const char * fmt, …)
Prints formatted output to string
int puts (const char * s)
Prints string to console
int scanf (const char * fmt, …)
Reads formatted input from console
int fgets (const char * s, FILE * stream)
Reads string from input stream 3

5. srand int printf (const char * format, …)
Writes formatted output to the console.
Use the %s format specifier for strings.
%s expects the address of a char array which contains a string.
Example:
char name[] = "Jane Doe";
printf("[%s]\n", name); → [Jane Doe]
printf("[%s]\n", &name[0]); → [Jane Doe]
printf("[%s]\n", &name[5]); → [Doe] 4

6. rand int sprintf (char * s, const char * format, …)
Performs a formatted print and saves it to a string.
Works like printf except the output is stored in string s.
Nothing is printed to the console.
Example:
char str[50];
int x = 4;
sprintf(str,"x=%d y=%f", x, 1.5f);
printf("title = %s\n", str); 5