IS 310 Chapter 6

What is the Little Man Computer (LMC)?

A simplified computer model used to demonstrate how a computer processes instructions and data.

How many mailboxes does the LMC have?

100 mailboxes, addressed from 00 to 99.

What can an LMC mailbox contain?

A 3-digit decimal number representing either data or an instruction.

What is the LMC calculator used for?

Holding values and performing arithmetic operations.

What does the LMC location counter do?

Identifies the address of the instruction to be fetched.

What are the two main parts of the LMC instruction cycle?

Fetch and execute.

What happens during the fetch part of the LMC instruction cycle?

The instruction is retrieved using the address in the location counter.

What happens during the execute part of the LMC instruction cycle?

The Little Man performs the operation required by the instruction.

What is an opcode?

The part of an instruction that identifies the task or operation to perform.

What is an operand in the LMC?

The two digits after the opcode that identify data or the address of data.

What are the major components of the CPU?

ALU, Control Unit, memory management unit, and I/O interface.

What does the ALU do?

Performs calculations and comparisons.

What does the Control Unit do?

Performs the fetch/execute cycle, runs instructions, and issues commands to the ALU.

What else does the Control Unit control?

It moves data between CPU registers and other hardware components.

What does the memory management unit do?

Supervises fetching instructions and data from memory.

What is a register?

A small permanent storage location inside the CPU used for a specific purpose.

What can a register hold?

Data, an address, or an instruction.

What are registers used for?

Holding information the CPU needs quickly while a program is executing.

What is the Program Counter (PC)?

A special-purpose register associated with the address of the next program instruction.

What is another name for the Program Counter?

Instruction Pointer (IP).

What is the Instruction Register (IR)?

A register that stores the instruction fetched from memory.

What is the Memory Address Register (MAR)?

A register that holds the address used to locate a memory location.

What is the Memory Data Register (MDR)?

A two-way register used to transfer data between the CPU and memory.

How do the MAR and MDR differ?

The MAR identifies the memory address; the MDR transfers the data to or from that location.

What is a status register?

A register that stores information about the CPU and the currently executing program.

What are flags in a status register?

One-bit Boolean variables used to track conditions such as arithmetic carry and overflow.

What happens when the CPU accesses memory?

The address goes to the MAR and data is transferred between memory and the MDR.

What is primary memory used for?

Holding program instructions and data needed for CPU execution.

What is secondary storage used for?

Long-term storage.