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title: "MC Programming: PUSHing and POPping (Part 7)"
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excerpt: "Seventh installment of the machine code series, covering the Z80 PUSH and POKE stack instructions for preserving register pairs during machine code subroutines. Explains how to avoid crashing the ZX80/81 by PUSHing registers before use and POPping before returning to BASIC. Includes three rules and FAST/SLOW mode notes."
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pubdate: "July 1982"
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---

# MC Programming: PUSHing and POPping (Part 7)

Seventh installment of the machine code series, covering the Z80 PUSH and POKE stack instructions for preserving register pairs during machine code subroutines. Explains how to avoid crashing the ZX80/81 by PUSHing registers before use and POPping before returning to BASIC. Includes three rules and FAST/SLOW mode notes.