Conditional jumps (except JCXZ/JECXZ) test the flags which have been set by a previous instruction. If the given condition is true, a jump is made to the location provided as the operand.
Instruction coding is most efficient when the target for the conditional jump is within -128 to +127 bytes of the next instruction's first byte (short jump). On the 80386+, the jump can also target -32768 through 32767 (segment size attribute 16) or -2 to the 31st power through +2 to the 31st power - 1 (segment size attribute 32) relative to the next instruction's first byte.
A condition code (cc) is associated with each instruction to indicate the condition being tested for. The terms "above" and "below" are used for un-signed integers; "less" and "greater" for signed integers. Note that several mnemonics have the same meaning.
Instruction Jump if ... Flags JA, JNBE Above, Not Below or Equal CF=0 AND ZF=0 JAE, JNB, JNC Above or Equal, Not Below, Not Carry CF=0 JBE, JNA Below or Equal, Not Above CF=1 OR ZF=1 JB, JC, JNAE Below, Carry, Not Above or Equal CF=1 JE, JZ Equal, Zero ZF=1 JNE, JNZ Not Equal, Not Zero ZF=0 JP, JPE Parity, Parity Even PF=1 JNP, JPO No Parity, Parity Odd PF=0
JG, JNLE Greater, Not Less or Equal SF=OF AND ZF=0 JGE, JNL Greater or Equal, Not Less SF=OF JLE, JNG Less or Equal, Not Greater SF<>OF OR ZF=1 JL, JNGE Less, Not Greater or Equal SF<>OF JO Overflow OF=1 JNO No Overflow OF=0 JS Sign (negative) SF=1 JNS No Sign (positive) SF=0
Opcode Format short; near; near; 'Near' forms available on 386+ 70 cb; 0F 80 cw; 0F 80 cd JO rel8/rel16/rel32 71 cb; 0F 81 cw; 0F 81 cd JNO rel8/rel16/rel32 72 cb; 0F 82 cw; 0F 82 cd JB rel8/rel16/rel32 73 cb; 0F 83 cw; 0F 83 cd JAE rel8/rel16/rel32 74 cb; 0F 84 cw; 0F 84 cd JE rel8/rel16/rel32 75 cb; 0F 85 cw; 0F 85 cd JNE rel8/rel16/rel32 76 cb; 0F 86 cw; 0F 86 cd JBE rel8/rel16/rel32 77 cb; 0F 87 cw; 0F 87 cd JA rel8/rel16/rel32 78 cb; 0F 88 cw; 0F 88 cd JS rel8/rel16/rel32 79 cb; 0F 89 cw; 0F 89 cd JNS rel8/rel16/rel32 7A cb; 0F 8A cw; 0F 8A cd JP rel8/rel16/rel32 7B cb; 0F 8B cw; 0F 8B cd JNP rel8/rel16/rel32 7C cb; 0F 8C cw; 0F 8C cd JL rel8/rel16/rel32 7D cb; 0F 8D cw; 0F 8D cd JGE rel8/rel16/rel32 7E cb; 0F 8E cw; 0F 8E cd JLE rel8/rel16/rel32 7F cb; 0F 8F cw; 0F 8F cd JG rel8/rel16/rel32