【Fujitsu】 MCP II

MCP (Master Control Program) was the control program for Fujitsu's medium general-purpose computers FACOM 230-20 and FACOM 230-30, and was made available in three models: MCP I, MCP II and MCP III. MCP II was the first control program for the company’s medium general-purpose computers to realize multiprogramming, and was completed in December 1966.
The following is the history of MCP development, together with an overview of MCP II.

1. Brief history of MCP

Previously, in program development, compile process and execution process were independent of each other, and switching between the two processes required considerable time and labor. To continuously execute jobs, the control program MCPI (Master Control Program I) was developed. Subsequently, MCP II and MCP III were successively developed. MCP II realized multiprogramming in order to increase the use efficiency of the computer (FACOM 230-20 and FACOM 230-30), and MCP III enabled small-scale real-time processing.
Table 1 shows the features and the completion dates of MCP models.
Table 1 Features and completion dates of MCP models
Name Features Required core memory Completion date
MCP I Control program for batch processing
The control program itself was placed on a magnetic tape or magnetic disk in order to avoid it occupying the memory during execution.
32/65k digits October 1965
MCP II Control program that realized multiple programming 65k digits December 1966
MCP III Control program that enabled two concurrent processes by improving MCP II. Two processes are one small-scale real-time process and one batch process, or two batch processes. The memory was divided into a batch program area and a real-time program area. The real-time program area was further divided into 16 segments to overlay programs. 32/65k digits June 1967

2. Overview of MCP II

(1) Features
MCP II was the first control program for Fujitsu’s medium-scale general-purpose computers to adopt multiprogramming, and provided the following features:
- Simultaneous processing of up to 4 programs
- Increased processing speed by making full use of a magnetic drum
- Simultaneous stack function up to 10 jobs to minimize operator intervention and increase operation efficiency
- Checkpoint and restart functions as an adequate measure against failure
(2) Software configuration and required equipment for the MCP II multiple programming system
The MCP II multiple programming system consisted of control program MCP II, a translation program (assembler FASP) under control of MCP II, service programs (FASP-CHECK, EDIT, UTILITY and SORT/MERGE) and user-created programs written in FASP language.
Table 2 shows the hardware equipment required for MCP II.
Table 2 Equipment required for MCP II
Item Name of equipment Number of units/capacity Remarks
1 FACOM 230-20 (or 230-30) central processing unit 1 unit  
2 Memory unit 65k digits  
3 Console/Typewriter unit 1 unit  
4 Paper tape reader or card reader 1 unit  
5 Magnetic drum unit 1 unit or none 1 unit recommended
6 Magnetic tape unit None or 2 units 2 units required if no magnetic drum unit.
Other than the equipment indicated in Table 2, at least 3 magnetic tape units and one line printer were required for the translation program and service programs.
(3) Structure of MCP II
MCP II consisted of two parts: MCP II supervisor program and MCP II monitor program.
The supervisor program was the core of the system, and the monitor program and the job programs (including the translation program and the service programs) were all executed under control of the supervisor program. The supervisor program consisted of two parts: an interrupt processing routine and SWITCHER, which provided the function to switch running programs.
The monitor program consisted of four parts: 1) keyboard instruction processing routine, 2) SCHEDULER, 3) INITIATOR and 4) TERMINATOR. The monitor program controlled interaction with the operator, management of job flows and management of some kind of the I/O devices.

Figure: Structure of the MCP II control program

Figure: Structure of the MCP II control program

(4) Effect of multiprogramming
MCP II was first used in the CM30 (FACOM 230-30) system delivered to Nippon Telegraph and Telephone Public Corporation in May 1967. When the multiprogramming function was used in bill printing processing, the number of bills to process was tripled and the increase of processing time was only 15%. Thus, the effect of multiprogramming was verified.
- Without multiple processing: processing approx. 4, 500 bills took 19 minutes, 23 seconds.
- Double processing (2 identical programs operated simultaneously): processing approximately 9,000 bills took 20 minutes, 33 seconds (+6%).
- Triple processing (3 identical programs operated simultaneously): processing approximately 13,500 bills took 22 minutes, 20 seconds (+15%).