The programming language a computer can directly execute is machine language (sometimes called "machine code"). Originally all programmers worked out every detail of the machine code, but this is hardly ever done anymore. Instead, programmers write source code, and a computer (running a compiler, an interpreter or occasionally an assembler) translates it through one or more translation steps to fill in all the details, before the final machine code is executed on the target computer. Even when complete low-level control of the target computer is required, programmers write assembly language, whose instructions are mnemonic one-to-one transcriptions of the corresponding machine language instructions.

The earliest programmable machine (that is, a machine that can adjust its capabilities based upon changing its "program") can be said to be the Jacquard Loom, which was developed in 1801. The machine used a series of pasteboard cards with holes punched in them. The hole pattern represented the pattern that the loom had to follow in weaving cloth. The loom could produce entirely different weaves using different sets of cards. This innovation was later refined by Herman Hollerith of IBM in the development of the famous IBM punch card.

Another early use of computer programs was made using a soldering iron and a large number of vacuum tubes (later transistors). As programs became more complex, this became almost impossible, as one mistake would likely render the whole program useless. As data storage media became more advanced, it became possible to re-use one program for many things according to the content of the memory. A person would spend quite some time making punch cards that would hold a list of instructions for a computer. Every model of computer would be likely to need different instructions to do the same task. As computers became more powerful, and storage media became re-usable, it became possible to use the computer to make the program. Programmers quickly began to favor text over 1s and 0s, and punch cards were phased out. As time has progressed computers have made giant leaps in the area of processing power. This has brought about newer programing languages that are more abstracted from the underlying hardware. Although these more abstracted languages require additional overhead, in most cases the huge increase in speed of modern computers has brought about little performance decrease compared to earlier counterparts. The benefits of these more abstracted languages is that they allow both an easier learning curve for people less familiar with the older lower-level programming languages, and they also allow a more experienced programmer to develop simple applications quickly. Despite these benefits, large complicated programs, and programs that are more dependent on speed still require the faster and relatively lower-level languages with todays hardware.