2018-01-28 19:00:23 +00:00
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Standard Library Functions for C02 Programs
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At the beginning of the program use the directives
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#include <stdlib.h02>
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The following functions are defined:
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c = abs(b); Returns the absolute value of the two's-complement
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byte b.
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In two's-complement arithmetic, the unsigned values
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0 - 127 are considered positive, while the unsigned
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values 128 - 255 are considered negative.
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c = atoc(&s); Returns the numeric value of the string in array s.
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Does not skip leading white-space characters and
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stops when first non-digit character is encountered.
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Overflows are ignored, so numbers greater than 255
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will be returned modulo 256.
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ctoa(c, &s); Stores the ASCII representation of usigned byte c
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as a null-terminated string in array s.
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The array must be dimensioned to at least 4 bytes.
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c = max(b, d); Returns the greater of the two unsigned bytes b and d.
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c = min(b, d); Returns the lesser of the two unsigned bytes b and d.
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c = mult(d, r); Returns the product of byte d times byte r.
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Overflows are ignored, so results greater than 255
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will be returned modulo 256.
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c = div(n, d); Returns the quotient of byte n divided by byte d.
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Remainders are discarded and division by 0 returns ??.
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c = rand(); Returns pseudo-random number. Sequence repeats
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after 255 repeated calls. The generator must be
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seeded using the rands() function before the first
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call to rand().
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rands(n); Seeds the pseudo-random number generator.
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If n is 0, the generator is seeded with a system
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seed value. This should be used for normal operation.
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If n is not 0. then it is used as the seed. This can
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be used for program testing or when a predictable
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pattern is needed.
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Note: The system seed is generated by a counter or
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timer. On systems that don't use a timer, the counter
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is cycled by the keyboard routines, so the getkey()
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or getchr() function must called at least once before
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a rands(0) call.
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c = shiftl(b, n); Returns byte b shifted n bits to the left, filling
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with 0's from the right.
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If n is greater than 8, all bits will be shifted out,
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and a value of 0 is treated as 256.
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c = shiftr(b, n); Returns byte b shifted n bits to the right, filling
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with 0's from the left.
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If n is greater than 8, all bits will be shifted out,
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and a value of 0 is treated as 256.
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Note: Using the shiftl() or shiftr() functions with
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an asignment generates 9 to 12 bytes of code, whereas
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the << and >> post-operators generate either 2 or 3
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bytes each. So for a constant number of shifts, the
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post-operators will generate smaller code for less
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than 5 shifts and will always be faster.
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2018-07-30 23:30:20 +00:00
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c = swap(b); Returns the byte b with the high and low nybbles
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swapped.
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2018-01-28 19:00:23 +00:00
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Note: This library expects the following function to be defined
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setsrc(&s); Set source string pointer and initialize index
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along with the zero page variables
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srclo,srchi: Source string pointer
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as well as the transient variables
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temp0 Temporary storage
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temp1
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temp2
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and the static variables
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random Psuedo-random number generator seed Value
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rdseed System generated initial seed (counter or timer)
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