The GPIB (General Purpose Interface Bus), or IEEE 488, is a bus designed to connect computers, peripherals and laboratory instruments so that data and control information can pass between them. It is defined in IEEE Standard 488.1 (1987) Standard Digital Interface for Programmable Instrumentation, with a particular view to ATE (Automatic Test Equipment).
The standard GPIB is a 16 line, bit parallel, byte serial bus. It has 8 lines to transfer the 8-bit data byte, and 3 lines to perform the handshake to guarantee a reliable data transfer. Another 5 lines are used for interface management. Fig. 1 shows the connector pin outline, and a summary of the GPIB lines is given in Table 1.
| Category | Line | Name |
| Data Lines | DIO1 to DIO8 | Data Input Output |
| Handshake Lines |
DAV | Data Valid |
| NRFD | Not Ready For Data | |
| NDAC | Not Data Accepted | |
| Interface Management Lines |
ATN | Attention |
| IFC | Interface Clear | |
| REN | Remote Enable | |
| SRQ | Service Request | |
| EOI | End or Identify |