Standard Library Functions for C02 Programs

At the beginning of the program use the directives

  #include <stdlib.h02>
  
The following functions are defined:

  c = abs(b);         Returns the absolute value of the two's-complement 
                      byte b.

                      In two's-complement arithmetic, the unsigned values 
                      0 - 127 are considered positive, while the unsigned 
                      values 128 - 255 are considered negative.

  c = atoc(&s);       Returns the numeric value of the string in array s. 
                      
                      Does not skip leading white-space characters and 
                      stops when first non-digit character is encountered.
                      
                      Overflows are ignored, so numbers greater than 255
                      will be returned modulo 256.

  ctoa(c, &s);        Stores the ASCII representation of usigned byte c 
                      as a null-terminated string in array s. 
                      
                      The array must be dimensioned to at least 4 bytes.

  c = max(b, d);      Returns the greater of the two unsigned bytes b and d.

  c = min(b, d);      Returns the lesser of the two unsigned bytes b and d.

  c = mult(d, r);     Returns the product of byte d times byte r.
  
                      Overflows are ignored, so results greater than 255
                      will be returned modulo 256.

  c = div(n, d);      Returns the quotient of byte n divided by byte d.
  
                      Remainders are discarded and division by 0 returns ??.

  c = rand();         Returns pseudo-random number. Sequence repeats 
                      after 255 repeated calls. The generator must be 
                      seeded using the rands() function before the first 
                      call to rand().
                      
  rands(n);           Seeds the pseudo-random number generator.

                      If n is 0, the generator is seeded with a system
                      seed value. This should be used for normal operation.
                      
                      If n is not 0. then it is used as the seed. This can
                      be used for program testing or when a predictable
                      pattern is needed.
                      
                      Note: The system seed is generated by a counter or 
                      timer. On systems that don't use a timer, the counter 
                      is cycled by the keyboard routines, so the getkey() 
                      or getchr() function must called at least once before 
                      a rands(0) call.

  c = shiftl(b, n);   Returns byte b shifted n bits to the left, filling
                      with 0's from the right.

                      If n is greater than 8, all bits will be shifted out,
                      and a value of 0 is treated as 256.

  c = shiftr(b, n);   Returns byte b shifted n bits to the right, filling
                      with 0's from the left.

                      If n is greater than 8, all bits will be shifted out,
                      and a value of 0 is treated as 256.
                      
                      Note: Using the shiftl() or shiftr() functions with
                      an asignment generates 9 to 12 bytes of code, whereas
                      the << and >> post-operators generate either 2 or 3
                      bytes each. So for a constant number of shifts, the
                      post-operators will generate smaller code for less 
                      than 5 shifts and will always be faster.

  c = swap(b);        Returns the byte b with the high and low nybbles
                      swapped.

Note: This library expects the following function to be defined

  setsrc(&s);         Set source string pointer and initialize index

along with the zero page variables
  
  srclo,srchi:        Source string pointer

as well as the transient variables
  
  temp0               Temporary storage
  temp1
  temp2
  
and the static variables

  random              Psuedo-random number generator seed Value
  rdseed              System generated initial seed (counter or timer)