A design of Text Editor in assembly language for SDK-85 (System Design Kit) unit of microprocessor 8085A to develop an INTELL'S 220 microcomputer system is proposed. As the name implies, a text editor permits a program to edit the program text. During the process of program entry into the memory or debugging, it may be necessary to make changes in the program text in order to correct any errors or modify the logic. In a microprocessor where a program is entered through keyboard. on the system console (with CRT), the program may enter the edit commands from the keyboards itself while entering the program. As the program statement are keyed in, they are simultaneously displayed on the CRT then by enabling the programmer to spot any keying errors immediately and correct them using the editor.