Jonathan Bobst

Articles (15)

TitleAuthor(s)PublicationDate
Beginners’ ML — Register to Register
Examines the loading, adding and subtracting instructions. Number 5 in series.
SyntaxMay 1982
Binary Addition and Subtraction
The point to learning how to add and subtract binary numbers is to see how “carries” are generated and what...
SyntaxFebruary 1982
Binary Representation
Knowing how to manipulate individual bits in your ZX80 is essential for efficient Machine Code programmming, so knowing what bits...
SyntaxJanuary 1982
Exchanging Registers, Part 6
In addition to the eight registers A,F,B,C,D,E,H and L covered in an earlier article, the Z80 (central processing unit in...
SyntaxJune 1982
How to Invent a Game – Inside Flattop Lander (MCD)
The conception and initial game design of Flattop Lander and the Machine Code subroutine that will produce an instant display.
SYNCJanuary/February 1982
How to Invent a Game, Part 2
Finishing the programming for the game.
SYNCMarch/April 1982
Loading Registers with Data (Part 4)
Fourth installment of the machine code programming series, covering Z80 load instructions: loading immediate data into registers (LD B,6), loading...
Jonathan BobstSyntaxApril 1982
Machine Code — CP Branching Tests
CPs are 1-3 byte codes that compare two numbers. More exactly, they subtract the number you are looking for from...
SyntaxAugust 1982
Machine Code Programming: #9, Testing Bits for Branching
You can test any bit in any address simply by loading a register and choosing the right instruction code.
SyntaxSeptember 1982
MC Programming #11: Storing MC Subroutines in REM
While you can store machine code subroutines anywhere in your BASIC program, the best place is 1 REM (& 2...
SyntaxNovember 1982
MC Programming #12: Calling and Returning
Tutorial on machine language programming.
SyntaxDecember 1982
MC Programming #9: Jumping Around
Most of the machine code subroutines held in REM will be be short around 100 instructions and data. Consequently, you...
SyntaxOctober 1982
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...
Jonathan BobstSyntaxJuly 1982
The Flags Register
Part 3 of series on machine code programming.
SyntaxMarch 1982
The Flags Register (Part 3)
Third installment of a 12-part machine code programming series. Explains the Z80 Flags register bits (Sign, Zero, Half-carry, Parity/Overflow, Add/Subtract,...
Jonathan BobstSyntaxMarch 1982

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