Each program is a sequence of instructions written in a programming language
Initially programming was based on entering of individual bits into memory.
Quickly it turned out that unreadable binary coding
was very inefficient, tedious and error-prone.

Soon, assemblers were created,
ie. languages to develop the program using human readable words.
Assemblers were a bit easier for programming but were still difficult to avoid errors of logic.

High-level languages have significantly increased readability of programs
and accelerated and ensured greater reliability of the code.

Above is a simple example illustrating the readability of the program
to calculate factorial in binary, assembler and high-level language.