The BBC and Master Computer Public Domain Library

AB4E ASCNUM (ASCII String to Binary Number)

Submitted by Steve Fewell

Routine:ascnum
Name: Convert ASCII string to Binary numbers
Starting Address: &AB4E
Entry: &36 = Length of String in SWA. SWA = ASCII Number "String".
Exit: A and &27 contain the conversion type (&40 = Integer; &FF = Float).

Description:

The ASCII string in SWA is converted to either an Integer (IWA)
or a Float (FWA).
The routine places a binary zero at the end of the SWA, and steps &36 by 1).
Push the text pointer B position onto the Hardware stack (PHA).
Read the text at the text pointer B position (offset from &0600).
Skip any spaces at PTR B.
if a '-' is the first character (sign) in the string then:      Skip any Spaces.
     Call &A2E1 to get the number (result).
     Then complement the result (if the carry is set - non-zero)
     Set &27 to the Result type and retore PTR B position from stack the return.
Otherwise; If a '+' is the first character found, then skip spaces and get next character
(and ignore the '+'-sign).
Call &A2E1 to get the numeric result.
Store the result type in &27.
restore the PTR B position and return with A=?&27.

Disassembly for the ASCNUM routine