The IBM 2501 is a
punched-card reader from IBM with models for the
System/360
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...
and
System/370
The IBM System/370 (S/370) is a model range of IBM mainframe computers announced on June 30, 1970, as the successors to the System/360 family. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path ...
mainframe
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...
systems and for the
IBM System/360 Model 20, the
IBM 1130
The IBM 1130 Computing System, introduced in 1965, was IBM's least expensive computer at that time. A binary 16-bit machine, it was marketed to price-sensitive, computing-intensive technical markets, like education and engineering, succeeding th ...
and
IBM System/3
The IBM System/3 was an IBM midrange computer introduced in 1969, and marketed until 1985. It was produced by IBM Rochester in Minnesota as a low-end business computer aimed at smaller organizations that still used IBM 1400 series computers or u ...
minicomputer
A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ' ...
s. 2501 models can read 80-column cards at either 600 or 1000 cards per minute (CPM).
The 2501 is no longer sold, but is simulated in software on current IBM systems.
Models
The 2501 comes in four models depending on speed and attachment features. Models for mainframe use come with an ''integrated control unit'' that performs the functions of a
control unit
The control unit (CU) is a component of a computer's central processing unit (CPU) that directs the operation of the processor. A CU typically uses a binary decoder to convert coded instructions into timing and control signals that direct the op ...
required by other devices.
The A1 and A2 are for the IBM 1130.
Usage
The 2501 uses a
photoelectric
The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...
sensor to read the data punched in the card. Cards are read ''serially'' (column by column) and the reader uses a simplified "straight through" card path. "Each column is read twice and the two readings are compared to check reading accuracy."
In a mainframe environment the 2501 was frequently used for mainframe input in an "open shop" environment where users submitted their own jobs.
On an 1130 system the 2501 can be used in addition to the
IBM 1442
IBM 1442 is a combination IBM card reader and card punch. It reads and punches 80-column IBM-format punched cards and is used on the IBM 1440, the IBM 1130, the IBM 1800 and System/360 and is an option on the IBM System/3.
Overview
The 1442 can ...
. Since the 1442 has a maximum speed of 300 or 400 CPM attaching a 2501 provides a significant increase in read speed and lower CPU usage.
The System/3 normally processes 96-column punched card; the 2501 provides alternative input for shops that require the ability to read 80-column cards.
Features
A
special feature (RPQ) is available for all models to allow them to read optically marked
(OMR) cards.
See also
*
Punched card input/output
A computer punched card reader or just computer card reader is a computer input device used to read computer programs in either source or executable form and data from punched cards. A computer card punch is a computer output device that punches ...
*
Computer programming in the punched card era
From the invention of computer programming languages up to the mid-1970s, most computer programmers created, edited and stored their programs line by line on punch cards.
Punched cards
A punched card is a flexible write-once medium that enco ...
References
{{Reflist
Computer peripherals
IBM mainframe peripherals
2501