| INT # | Locus | Function |
| 0 | CPU | divide by zero |
| 1 | CPU | single step |
| 2 | CPU | non-maskable |
| 3 | CPU | breakpoint |
| 4 | CPU | overflow trap |
| 5 | BIOS | print screen |
| 6 | CPU | Invalid opcode (186,286,386) |
| 7 | CPU | coprocessor not available (286,386) |
| 8 | IRQ0 | timer (55ms intervals, 18.21590 per second) |
| 9 | IRQ1 | keyboard service required (see INT 9) |
| A | IRQ2 | slave 8259 or EGA/VGA vertical retrace |
| B | IRQ3 | COM2 service required (PS/2 MCA COM3-COM8) |
| C | IRQ4 | COM1 service required |
| D | IRQ5 | fixed disk or data request from LPT2 |
| E | IRQ6 | floppy disk service required |
| F | IRQ7 | data request from LPT1 (unreliable on IBM mono) |
| 10 | BIOS | video (see INT 10) |
| 11 | BIOS | Equipment determination (see <A HREF=“int_11.html”>INT 11</A>) |
| 12 | BIOS | memory size (see <A HREF=“int_12.html”>INT 12</A>) |
| 13 | BIOS | disk I/O service (see <A HREF=“int_13.html”>INT 13</A>) |
| 14 | BIOS | serial communications (see <A HREF=“int_14.html”>INT 14</A>) |
| 15 | BIOS | system services, cassette (see <A HREF=“int_15.html”>INT 15</A>) |
| 16 | BIOS | keyboard services (see <A HREF=“int_16.html”>INT 16</A>) |
| 17 | BIOS | parallel printer (see <A HREF=“int_17.html”>INT 17</A>) |
| 18 | BIOS | ROM BASIC loader |
| 19 | BIOS | bootstrap loader (unreliable, see <A HREF=“int_19.html”>INT 19</A>) |
| 1A | BIOS | time of day (see <A HREF=“int_1a.html”>INT 1A</A>) |
| 1B | BIOS | user defined ctrl-break handler (see <A HREF=“int_1b.html”>INT 1B</A>) |
| 1C | BIOS | user defined clock tick handler (see <A HREF=“int_1c.html”>INT 1C</A>) |
| 1D | BIOS | 6845 video parameter pointer |
| 1E | BIOS | diskette parameter pointer (base table) |
| 1F | BIOS | graphics character table |
| 20 | DOS | general program termination |
| 21 | DOS | function request services (see INT 21) |
| 22 | DOS | terminate address (see <A HREF=“int_22.html”>INT 22</A>) |
| 23 | DOS | control break termination address (see <A HREF=“int_23.html”>INT 23</A>) |
| 24 | DOS | critical error handler (see <A HREF=“int_24.html”>INT 24</A>) |
| 25 | DOS | absolute disk read (see <A HREF=“int_25.html”>INT 25</A>) |
| 26 | DOS | absolute disk write (see <A HREF=“int_26.html”>INT 26</A>) |
| 27 | DOS | terminate and stay resident (see <A HREF=“int_27.html”>INT 27</A>) |
| 28 | DOS | idle loop, issued by DOS when idle (see <A HREF=“int_28.html”>INT 28</A>) |
| 29 | DOS | fast TTY console I/O (see <A HREF=“int_29.html”>INT 29</A>) |
| 2A | DOS | critical section and NETBIOS (see <A HREF=“int_2a.html”>INT 2A</A>) |
| 2B | DOS | internal, simple <A HREF=“iret.html”>IRET</A> in DOS 2.0-5.0 |
| 2C | DOS | internal, simple IRET in DOS 2.0-5.0 |
| 2D | DOS | internal, simple IRET in DOS 2.0-5.0 |
| 2E | DOS | exec command from base level command interpreter (see <A HREF=“int_2e.html”>INT 2E</A>) |
| 2F | DOS | multiplexer (see <A HREF=“int_2f.html”>INT 2F</A>) |
| 30-31 | CPM | far jump vector for CPM (not an interrupt) |
| 31 | DPMI | DOS Protected Mode Interface (for DOS extenders) |
| 32 | | reserved |
| 33 | | mouse support (see <A HREF=“int_33.html”>INT 33</A>) |
| 34-3E | | Microsoft/Borland floating point emulation |
| 3F | | overlay manager |
| 40 | BIOS | hard disk |
| 41 | BIOS | fixed disk 0 parameters pointer (see <A HREF=“int_13-9.html”>INT 13,9</A>) |
| 42 | BIOS | relocated video handler (EGA/VGA/PS) |
| 43 | BIOS | user font table (EGA/VGA/PS) |
| 44 | BIOS | first 128 graphics characters (also Netware) |
| 45 | BIOS | reserved for BIOS |
| 46 | BIOS | fixed disk 1 parameters ptr (see <A HREF=“int_13-9.html”>INT 13,9</A>/INT 41) |
| 47 | BIOS | reserved for BIOS |
| 48 | BIOS | PCjr cordless keyboard translation |
| 49 | BIOS | PCjr non-keyboard scancode translation table |
| 4A | BIOS | user alarm (AT,CONV,PS/2) (see <A HREF=“int_4a.html”>INT 4A</A>) |
| 4B-4F | BIOS | reserved |
| 50 | BIOS | periodic alarm from timer (PS/2) |
| 51-58 | BIOS | reserved |
| 59 | BIOS | GSS Computer Graphics Interface |
| 5A | BIOS | cluster adapter BIOS entry point |
| 5B | BIOS | cluster adapter boot |
| 5C | NETBIOS | NETBIOS interface, TOPS interface |
| 5D-5F | BIOS | reserved for BIOS |
| 60-67 | | reserved for user software interrupts |
| 67 | EMS | LIM/EMS specification (see <A HREF=“int_67.html”>INT 67</A>) |
| 68 | | APPC |
| 69-6B | | reserved by IBM |
| 6C | DOS | DOS 3.2 real time clock update |
| | BIOS | system resume vector |
| 6D-6F | | reserved |
| 70 | IRQ8 | real time clock (AT,XT286,PS50+, see <A HREF=“int_15.html”>INT 15</A>) |
| 71 | IRQ9 | software redirected to IRQ2 (AT,XT286,PS50+) |
| 72 | IRQ10 | reserved (AT,XT286,PS50+) |
| 73 | IRQ11 | reserved (AT,XT286,PS50+) |
| 74 | IRQ12 | mouse interrupt (PS50+) |
| 75 | IRQ13 | numeric coprocessor NMI error (AT,XT286,PS50+) |
| 76 | IRQ14 | fixed disk controller (AT,XT286,PS50+) |
| 77 | IRQ15 | reserved (AT,XT286,PS50+) |
| 78-79 | | unused |
| 80-85 | | ROM BASIC |
| 86-F0 | DOS | reserved for BASIC interpreter use |
| 86 | NETBIOS | NETBIOS relocated INT 18 |
| E0 | CPM | CP/M 86 function calls |
| F1-FF | | reserved by IBM |
| FE-FF | | may be destroyed by return from protected mode using VDISK on 286 machines (Apr 86, DDJ) |