Conditional branch with flags in ARM Architecture - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a conditional branch in ARM architecture?

A conditional branch is an instruction that changes the flow of execution only if certain conditions, based on processor flags, are met.

beginner

Which processor flags are commonly used for conditional branching in ARM?

The common flags are N (Negative), Z (Zero), C (Carry), and V (Overflow). These flags reflect the result of previous operations.

beginner

How does the Zero (Z) flag affect conditional branching?

If the Z flag is set (meaning the last result was zero), a branch instruction with a condition checking Z will execute the branch.

beginner

What does the 'BEQ' instruction do in ARM assembly?

BEQ stands for 'Branch if Equal'. It causes a branch if the Zero (Z) flag is set, indicating the previous comparison found equality.

beginner

Why are flags important for conditional branches?

Flags store results of operations like comparisons. Conditional branches use these flags to decide if the program should jump to a different part of code.

Which flag indicates if the last operation result was zero?

A Z (Zero)

B N (Negative)

C C (Carry)

D V (Overflow)

The Z flag is set when the result of the last operation is zero.

What does the ARM instruction 'BNE' do?

A Branch if Negative

B Branch if Not Equal

C Branch if Equal

D Branch if Overflow

BNE branches if the Zero flag is clear, meaning the compared values were not equal.

Which flag is set when an arithmetic operation results in a negative number?

A N (Negative)

B C (Carry)

C V (Overflow)

D Z (Zero)

The N flag is set when the result of an operation is negative.

What does the 'BGT' instruction check before branching?

A Branch if Greater Than (checks Z flag only)

B Branch if Greater Than (checks C flag only)

C Branch if Greater Than (checks N and V flags)

D Branch if Greater Than (ignores flags)

BGT branches if the result is greater than, which involves checking the Negative and Overflow flags along with Zero.

If the Carry (C) flag is set, what does it usually indicate?

A An overflow occurred

B The last result was zero

C The result was negative

D A carry out from the last addition or borrow in subtraction

The Carry flag is set when there is a carry out from addition or borrow in subtraction.

Explain how conditional branches use flags in ARM architecture to control program flow.

Think about how the processor decides to jump or continue based on previous results.

Describe the role of the Zero (Z) and Negative (N) flags in conditional branching.

Consider what these flags tell about the last operation's outcome.