Chapter 14 - Assembly Language

A mnemonic is a letter representation of machine code

A numeric code consists of 3 characters. ADD’s numeric code is 1xx. The first character is an OP code (which defines the function of mnemonic) and the xx is the operand which describes the memory address/value the OP code functions upon.

Mnemonic: ADD Adds the contents of the memory address to the accumulator

Mnemonic: SUB Subtracts the contents of the memory address from the accumulator

Mnemonic: STA Stores the value in the accumulator in the memory address given

Mnemonic: LDA Load the accumulator with the contents of the memory address given.

Mnemonic: BRA Branch - always uses the address given as the address of the next instruction (by changing PC).

Mnemonic: BRZ Branch to the address given if the accumulator is zero

Mnemonic: BRP Branch to the address given if the accumulator is zero or positive

Mnemonic: INP Input into the accumulator

Mnemonic: OUT Output contents of the accumulator

Mnemonic: HLT Stops the execution of the program

Mnemonic: DAT Used to indicate a location that contains data.

Branch (unconditional) - BRA, Branch if zero (conditional) - BRZ, Branch if positive (conditional) - BRP.

The last 2 digits within the operation code (OP code)

intermediate addressing: the operand is the actual value upon which the instruction is to be performed upon direct addressing: the operand holds the memory address location of the value to be operated upon (only mode available in LMC) indirect addressing: the operand is the location (typically a register) which holds the address we want - a larger range of accessible locations indexed addressing: the address of the operand is obtained by adding the contents of a general register (index register) to a constant value. Included in istruction code and used to access arrays with successive order

When you write something in LMC, the specific line you write it on means that it gets stored within that memory address location in RAM.