Generate a random number with C

Thank you for your answers, they really helped me :)

What i did is that is ask the user to press a button to start using the program.

Until the user presses the button, a variable increments itself.

I show you my code :

do
    {
        if(*switches==0)
        {
            LCD_Test("Switch up SW0", "To continue");
            while(*switches==0)
            {
                if(highPrecisionTimer>100000000)
                    highPrecisionTimer=0;
                    
                highPrecisionTimer++;
            }
            keepGoing = 1;
        }
        else if(*switches==1)
        {
            LCD_Test("Switch down SW0", "To continue");
            while(*switches==1)
            {
                if(highPrecisionTimer>100000000)
                    highPrecisionTimer=0;
               highPrecisionTimer++;
            }
            keepGoing = 1;
        }
            
    }while(keepGoing != 1);
srand(highPrecisionTimer);

So now my rand() function works.

Thank you !