And EXecute was part of the original System 360 instruction set in 1964.
As were facilities for checking to see if a value exceeded 255. /Charles/ +1-707-291-0908 On 3/30/2026 11:10 AM, Martin Ward wrote:
I recently worked on some code which included a variable length compare. The length was provided in a halfword which was decremented and then ORed into the first two bytes of a CLC instruction. There are no checks for a length greater than 256: so it would just overwrite the opcode. I imagine the programmer muttering "I don't hold with these 'ere new-fangled `long' instructions like CLCL. 256 bytes ought to be enough for anyone." (CLCL was introduced in 1970).
