A microassembler is a type of software used to design the control unit of a computer. It generates a microprogram from text written by a programmer. It is often called a meta-assembler. It is different from an ordinary assembler becaue the position and widths of the fields in a micro-instruction will depend of the design of the hardware. The meta-assembler contains an extra stage in which the widths and positions of the fields are defined. It is then possible to write the microcode. The microprogram is then loaded to a control store to become of the logic of a CPU's control unit.