Carry Flag

In computer processors the carry flag (usually indicated as the C flag) is a single bit in a system status (flag) register used to indicate when an arithmetic carry or borrow has been generated out of the most significant ALU bit position. The carry flag enables numbers larger than a single ALU width to be added/subtracted by carrying (adding) a binary digit from a partial addition/subtraction to the least significant bit position of a more significant word. It is also used to extend bit shifts and rotates in a similar manner on many processors (sometimes done via a dedicated X flag). For subtractive operations, two (opposite) conventions are employed as most machines sets the carry flag on borrow while some machines (such as the 6502 and the PIC) instead resets the carry flag on borrow (and vice versa).

Read more about Carry FlagUses, Carry Flag Vs. Borrow Flag

Other articles related to "carry flag, flag, carry, flags":

Carry Flag Vs. Borrow Flag
... While the carry flag is well-defined for addition, there are two possible ways to use the carry flag for subtractive operations ... One uses the bit as a borrow flag, setting it if a ...
FCMOV - Variants
... Meaning Condition DA C0+i FCMOVB Move if below Carry flag set DA C8+i FCMOVE Move if equal Zero flag set DA D0+i FCMOVBE Move if below or equal Carry flag or Zero flag ...
Intel BCD Opcode - Usage - Subtraction
... First the numbers are subtracted as usual using sub (or sbb if you need the carry flag) ... Packed The processor will have set the adjust flag if a borrow occurred in the least significant nibble, and the carry flag if a borrow occurred in the most significant nibble ... If the least significant nibble of the result is 10 or higher, or if the adjust flag is set, then the processor subtracts 6 from the result ...
X86 Instructions - X86 Integer Instructions - Original 8086/8088 Instructions
... is documented, see notes for AAD AAS ASCII adjust AL after subtraction ADC Add with carry destination = destination + source + carry_flag ADD Add (1) r/m += r/imm (2) r += m/imm AND. 0x0F POPF Pop data from flags register PUSH Push data onto stack *--SP = r/m PUSHF Push flags onto stack *--SP = flags RCL Rotate left (with carry) RCR Rotate right (with carry) REPxx Repeat MOVS/STOS/CMPS/LODS/SCAS (RE ... procedure ROL Rotate left ROR Rotate right SAHF Store AH into flags SAL Shift Arithmetically left (signed shift left) (1) r/m = CL SBB Subtraction with borrow ...
Bit Bucket
... Some CPUs move the last bit shifted off the end of a number during a shift into the carry flag during some or all shift operations since the bit bucket is usually considered the ...

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