CMOVB

CMOVB is a conditional move instruction found in x86 assembly language. The mnemonic CMOV signifies "Conditional Move." The "B" suffix indicates that the condition being checked is "below." Specifically, CMOV B moves the contents of a source operand to a destination operand only if the "below" condition is true. This condition is determined by the state of the Carry Flag (CF) in the processor's flags register. The CMOV B instruction executes if the Carry Flag is set (CF = 1). This typically occurs after arithmetic operations where an unsigned subtraction resulted in a borrow, or an unsigned addition caused a carry out.

Unlike a jump instruction that alters the program flow, CMOV B conditionally updates the destination operand without changing the instruction pointer. This allows for branching logic to be implemented without the overhead of a jump, potentially leading to performance improvements by avoiding pipeline flushes. The source and destination operands for CMOV B are typically general-purpose registers or memory locations. It's important to note that CMOV B is a conditional instruction and its execution depends on the result of a prior arithmetic or logical operation that affects the Carry Flag.