Branching
Branching is the process of executing a different sequence of instructions.
Instructions
The following are instructions relevant to branching.
| Instruction | Description |
|---|---|
| BRA | Branches to the given memory address. |
| BRZ | Branches to the given memory address, if the value in the Accumulator is 0. |
Example (improved_calc)
Continuing with the trend of a calculator, let’s build a dual-purpose calculator using the skills learnt above.
START INP # Waits for input and stores it in the accumulator
STA MODE # Stores the contents of the accumulator into the memory location of the label: MODE
INP # Waits for input and stores it in the accumulator
STA VALUE_O # Stores the contents of the accumulator into the memory location of the label: VALUE_O
INP # Waits for input and stores it in the accumulator
STA VALUE_T # Stores the contents of the accumulator into the memory location of the label: VALUE_T
LDA MODE # Loads the contents of the memory location of the label: MODE to the accumulator
BRZ ADDITION # Branches to the memory location of the label: ADDITION is the contents of the accumulator are 0
BRA SUBTRACT # Branches to the memory location of the label: SUBTRACT
ADDITION LDA VALUE_O # Loads the contents of the memory location of the label: VALUE_O to the accumulator
ADD VALUE_T # Add the contents of memory address of the label: NUM to the accumulator
BRA END # Branches to the memory location of the label: END
SUBTRACT LDA VALUE_O # Loads the contents of the memory location of the label: VALUE_O to the accumulator
SUB VALUE_T # Subtract the contents of memory address of the label: NUM to the accumulator
BRA END # Branches to the memory location of the label: END
END OUT # Outputs the contents of the accumulator
HLT # Signify the end of the program
MODE DAT 1 # Defines the label: MODE as containing data, and sets it to a preset of 1
VALUE_O DAT 1 # Defines the label: VALUE_O as containing data, and sets it to a preset of 1
VALUE_T DAT 2 # Defines the label: VALUE_T as containing data, and sets it to a preset of 2