A 4-bit microprocessor is a type of computer processor that can process data in 4-bit chunks. This means it can handle binary numbers that are 4 bits long, allowing it to perform basic arithmetic and logic operations. These microprocessors are often used in simple devices like calculators and early computers, where complex processing power is not required. The architecture of a 4-bit microprocessor includes a small number of registers and a simple instruction set. Popular examples include the Intel 4004 and the TMS 1000. While they are not commonly used today, they laid the groundwork for the development of more advanced processors, leading to the powerful systems we use now.