NEC successively shipped the MOD series operating systems (MOD I, MOD III, MOD IV and MOD VII) for the NEAC-series 2200, which was developed in technical collaboration with Honeywell of the United States. MOD I through MOD III were developed using technology introduced by Honeywell. NEC independently developed MOD IV and higher OSs as full-scale operating systems. The MOD series took full advantage of the one-machine concept, and all OSs in the series, from MOD I through MOD VII, provided compatibility and expandability of data files and application programs.
MOD I was designed for small machines, and two versions were offered: one for magnetic tape systems and the other for disk systems. MOD III and higher OSs were designed for medium-to-large machines. They were powerful software programs that incorporated features such as simultaneous processing of multiple independent programs, dynamic allocation of memory and I/O devices, high-level languages including COBOL and FORTRAN, time-sharing system (NEAC-TSS) and CRJE (Conversational Remote Job Entry), and provided a broad range of services according to the application operations and equipment configurations required by specific users.
| Name of OS | Features | Models that could use the OS |
|---|---|---|
| MOD I-TR | Had a multi-program processing function in which conversion of one set of data for individual job control and batch programming were performed simultaneously, together with a function to effectively operate a system centered on a magnetic tape device. | Models 50 to 500 |
| MOD I-MSR | Capable of easily performing inline processing and online processing due to NOSS-7 (NEAC Online Software System) in addition to batch processing with a system centered on a magnetic disk device. | Models 75 to 500 |
| MOD III | Had functions (e.g., stacked job processing) to effectively use multiple programs (4 programs) and a large computer system in addition to the functions of MOD I-TR and MSR. | Models 375 to 500 |
| MOD IV | Had a function to perform up to 20 programs including stacked job processing, online real-time processing and remote job processing. | Models 250 to 700 |
| MOD IV EX | Had a function to effectively operate a system centered on a high-speed magnetic drum device in addition to the functions of MOD IV. | Models 575 to 700 |
| MOD VII | Had a function to effectively operate a multi-processor system. | Model 700 |