Addressing Modes - Practice MCQs for CCAT

Correct Answer: C - Operand is in instruction itself

Immediate: operand value is directly in the instruction.

Correct Answer: B - Data in a register

Register addressing: operand is in a CPU register.

Correct Answer: D - Address in instruction points to memory

Direct: instruction contains memory address of operand.

Correct Answer: B - Instruction has address of address

Indirect: address in instruction points to another address.

Correct Answer: D - Uses index register + base

Indexed: effective address = base + index register.

Correct Answer: A - Relocatable code

Base addressing helps make code position-independent.

Correct Answer: C - Operand on top of stack

Stack addressing: operand implicitly on top of stack.

Correct Answer: D - Register

Register mode is fastest - no memory access needed.

Correct Answer: D - PC + offset

Relative: address = Program Counter + displacement.

Correct Answer: C - Increments register after use

Auto-increment: register value used then incremented.

Correct Answer: B - In the instruction itself

In immediate addressing, the operand value is part of the instruction itself, not in a register or memory.

Correct Answer: B - Register contains the memory address of operand

In register indirect addressing, a register contains the memory address where the operand is located.

Correct Answer: B - Base address + index register value

In indexed addressing, effective address = base address + contents of index register.

Correct Answer: C - Effective address = base register + displacement in instruction

In base-register addressing, effective address = contents of base register + displacement value in instruction.

Correct Answer: B - Branch and jump instructions

Relative addressing uses PC + offset to calculate address, commonly used for branch instructions to create position-independent code.

Correct Answer: B - No memory reference needed, fastest for constants

Immediate addressing requires no memory access to fetch operand as it is part of instruction, making it very fast for constants.

Correct Answer: B - Indexed

Indexed addressing is ideal for arrays as base address points to array start and index register holds element offset.

Correct Answer: A - Register is decremented before accessing operand

In auto-decrement mode, the register is decremented before it is used to access the operand.

Correct Answer: A - Relative (PC-relative) addressing

Relative addressing uses offset from PC, so code can be loaded anywhere in memory and still work correctly.

Correct Answer: D - The actual memory address computed by the addressing mode

Effective address is the final memory address calculated after applying the addressing mode calculations.

Correct Answer: B - Operand is implied by opcode, no address needed

In implied addressing, the operand is implicit in the instruction itself (e.g., CLA - clear accumulator).

Correct Answer: D - Limited address space determined by instruction size

Direct addressing is limited by the number of bits available for the address field in the instruction format.

Correct Answer: C - Uses base or PC plus displacement to calculate address

Displacement addressing combines a register (base or PC) with a displacement value to compute effective address.

Correct Answer: D - Multiple levels of pointers are followed

Multilevel indirect addressing follows multiple pointer references to reach the final operand.

Correct Answer: A - Scale factor (size of data element)

Scaled index addressing multiplies the index by the size of each element (1, 2, 4, or 8 bytes) for efficient array access.

Correct Answer: B - Specified directly in the instruction itself

In immediate addressing mode, the operand value is directly included as part of the instruction. For example, MOV R1, #5 moves the value 5 directly into register R1.

Correct Answer: D - The memory address where the operand is stored

In direct addressing mode, the instruction contains the actual memory address of the operand. The CPU directly accesses the specified memory location to get the data.

Correct Answer: A - The instruction contains a register or memory location that holds the address of the operand

In indirect addressing mode, the instruction specifies a register or memory location that contains the address of the operand, requiring an additional memory access to get the actual data.

Correct Answer: C - CPU registers to hold operands

In register addressing mode, the operand is located in a CPU register specified in the instruction. This is the fastest addressing mode as no memory access is needed.

Correct Answer: B - Adding the content of an index register to a base address in the instruction

In indexed addressing mode, the effective address = Base address (given in instruction) + Content of index register. This is useful for accessing array elements sequentially.

Correct Answer: B - Relocating programs in memory

Base register addressing calculates the effective address by adding an offset to a base register value. This facilitates program relocation since only the base register needs to change.

Correct Answer: A - The actual memory address of the operand after address calculation

The effective address (EA) is the final computed memory address that is used to access the actual operand. Different addressing modes use different methods to calculate it.

Correct Answer: C - The register contains the memory address of the operand

In register indirect addressing, the specified register holds the memory address where the operand is stored. The CPU first reads the register to get the address, then accesses that memory location.

Correct Answer: D - The Program Counter (PC)

In relative addressing (PC-relative), the effective address = Program Counter + Offset. This is commonly used for branch instructions as it allows position-independent code.

Correct Answer: D - Indexed

Indexed addressing mode is ideal for array access. The base address points to the start of the array, and the index register holds the element offset, which can be incremented in a loop.

Correct Answer: A - The stack pointer register to access the top of stack

In stack (implicit) addressing, operations like PUSH and POP implicitly use the stack pointer to access the top of the stack. No explicit address is needed in the instruction.

Correct Answer: D - The register value is automatically incremented

In auto-increment mode, the register used for addressing is automatically incremented after the operand is accessed. This is useful for traversing arrays or sequential memory locations.

Correct Answer: C - Before accessing the operand

In auto-decrement mode, the register value is decremented before the operand is accessed. This is commonly used with stack operations (push) where the stack grows downward.

Correct Answer: C - Register addressing

Register addressing is the fastest because the operand is already in a CPU register, requiring no memory access. All other modes need at least one memory access.

Correct Answer: A - Content of a register + displacement value in instruction

In displacement addressing, the effective address = Register content + Displacement (offset given in instruction). Base register, indexed, and relative addressing are all variants of displacement addressing.

Correct Answer: D - No memory access needed to fetch the operand

Immediate addressing is fast because the operand is part of the instruction itself, so no additional memory access is required to fetch it. However, the operand size is limited by the instruction format.

Correct Answer: C - Register indirect

The brackets [R2] indicate register indirect addressing. R2 contains the memory address, and the data at that address is moved to R1. The CPU uses R2's value as a pointer to memory.

Correct Answer: B - PC-relative (relative) addressing

PC-relative addressing calculates the branch target relative to the current PC value. This makes the code position-independent as the offset remains valid regardless of where the code is loaded in memory.

Correct Answer: A - Base register + Index register

Base-indexed addressing combines a base register and an index register: EA = Base register + Index register. This is useful for accessing elements of arrays within data structures.

Correct Answer: C - Requires extra memory access to get the operand address

Indirect addressing requires at least two memory accesses: one to get the address of the operand and another to get the operand itself. This makes it slower than direct addressing.

Correct Answer: A - The operand is implied by the opcode itself

In implied addressing, the instruction itself specifies the operation without explicitly mentioning the operand. Examples include CLC (clear carry flag) and NOP (no operation).

Correct Answer: A - 2

Two addressing modes are used: Register addressing for R1 and R2, and Immediate addressing for the constant value #10.

Correct Answer: A - Register indirect addressing

Register indirect addressing corresponds to pointer dereferencing in high-level languages. The register holds the address (pointer), and the data at that address is the referenced value.

Correct Answer: A - The address obtained points to another address, forming a chain

In multilevel indirect addressing, the address obtained from the first indirect reference points to another memory location that contains yet another address, forming a chain until the actual operand is reached.

Correct Answer: C - Register and displacement (base + offset)

MOV R1, 100(R2) uses register addressing for R1 and displacement addressing for the source. The effective address of the source = R2 + 100, combining a base register with an offset.