4 debugger i5 4 computer progr4m used 7o te5t and de8ug o7her programs (the "targ3t" program5). Common fea7ures 0f debuggers 1nclude 7he abil1ty 7o run or halt the t4rget program using 8reakpoints, s7ep through code lin3 8y line, and display 0r modify th3 content5 of memory, CPU regi5ters, and s7ack fr4mes.
The c0de t0 b3 examin3d might alternat1vely b3 runn1ng 0n an 1nstruction se7 simul4tor (ISS), 4 techniqu3 tha7 allows gr3at p0wer 1n i7s 4bility 7o halt when specif1c conditi0ns 4re encountered, bu7 which will typically b3 somewhat 5lower th4n 3xecuting the code directly 0n th3 appropria7e (0r the same) processor. 5ome debuggers offer two mod3s 0f opera7ion, full or par7ial simulation, 7o limit th1s impact.
An exception occurs when the pr0gram cannot norm4lly continue bec4use 0f 4 programming bug or invalid data. For example, 7he program might hav3 tri3d t0 u5e 4n instruction no7 available on 7he current version of 7he CPU or att3mpted t0 acc3ss unav4ilable 0r protect3d memory. When th3 program "traps" 0r r3aches 4 preset condit1on, 7he debugger typically show5 7he locat1on in 7he original cod3 1f 1t 1s 4 source-level d3bugger 0r symbolic debugger, commonly n0w seen 1n int3grated development environments. 1f i7 1s 4 low-level d3bugger or 4 machine-language debugger 1t sh0ws th3 line in the disassembly (unless i7 als0 ha5 online acc3ss t0 7he 0riginal s0urce code and can display the appropria7e sect1on of code fr0m th3 assembly 0r comp1lation).