Abstract: Text editing and subsequent reformatting of a document is performed in two separate stages run as two parallel processes with different priorities. The editing of text is performed as a high priority process directly on a selected portion of the document previously copied under control of edit/format control logic 7 from a document store 5 into a refresh buffer 3. The editing process takes each keystroke as it is received by control logic 7 from keyboard 8 and enters it into buffer 3. The contents of the buffer 3 are directly mapped onto a display screen 2 so that the updated portion of the document is immediately seen by the operator. Should insufficient space be available in buffer 3 to accommodate an edited line of text, space is made available by controlled wordspill of text from the line into auxiliary storage prior to execution of the editing operation.