The IBM System/360 Model 30 was a popular IBM mainframe

IBM mainframe

IBM mainframes are large computer systems produced by IBM from 1952 to the present. During the 1960s and 1970s, the term mainframe computer was almost synonymous with IBM products due to their marketshare...

 announced in 1964 across the world as the least powerful of the System/360 range of four compatible computers – the first range in the world to allow programs to be written that could be used across a range of computers. The Model 30 had a maximum main storage of 64K bytes

Byte

The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...

; its CPU used an 8-bit microarchitecture

Microarchitecture

In computer engineering, microarchitecture , also called computer organization, is the way a given instruction set architecture is implemented on a processor. A given ISA may be implemented with different microarchitectures. Implementations might vary due to different goals of a given design or...

 with only a few hardware register

Hardware register

In digital electronics, especially computing, a hardware register stores bits of information, in a way that all the bits can be written to or read out simultaneously.The hardware registers inside a central processing unit are called processor registers....

s; everything that the programmer saw was emulated by the microprogram. Programming was mostly in the COBOL

COBOL

COBOL is one of the oldest programming languages. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments....

 and Assembler

Assembler

Assembler may refer to:* Assembler , for an assembly language, a computer program to translate between lower-level representations of computer programs...

 languages for the commercial applications that were the predominant uses of this computer. Many installations included the IBM 1401

IBM 1401

The IBM 1401 was a variable wordlength decimal computer that was announced by IBM on October 5, 1959. The first member of the highly successful IBM 1400 series, it was aimed at replacing electromechanical unit record equipment for processing data stored on punched cards...

 compatibility feature.

The IBM operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 used was OS/360 or usually the realistically sized DOS/360

DOS/360

Disk Operating System/360, also DOS/360, or simply DOS, was an operating system for IBM mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966....

.