Implications of Structured Programming for Machine Architecture Based on an empirical study of more than 10,000 lines of program text written in a GOTO-less language, a machine architecture specifically designed for structured programs is proposed. Since assignment, CALL, RETURN, and IF statements together account for 93 percent of all executable statements, special care is given to ensure that these statements can be implemented efficiently. A highly compact instruction encoding scheme is presented, which can reduce program size by a factor of 3. Unlike a Huffman code, which utilizes variable length fields, this method uses only fixed length (1-byte) op code and address fields. The most frequent instructions consist of a single 1-byte field. As a consequence, instruction decoding time is minimized, and the machine is efficient with respect to both space and time. CACM March, 1978 Tanenbaum, A. machine architecture, computer architecture, computer organization, instruction set design, program characteristics 4.12 4.22 4.9 6.21 CA780308 JB March 28, 1978 12:55 PM 2411 4 3005 2709 4 3005 2889 4 3005 2937 4 3005 2989 4 3005 3005 4 3005 3025 4 3005 3101 4 3005 2138 5 3005 3005 5 3005 3005 5 3005 3005 5 3005