What is Mainframe Computer? Uses, Types & More

What is Mainframe Computer

What is Mainframe Computer?

A mainframe computer, also known as mainframe simply is the frame that holds a lot of processors and the RAM. Technically, a mainframe computer refers to a large and powerful system made with the combination of several processors and memory.

A mainframe computer also refers to the CPU of several terminals and workstations that are connected with it that allows several users to use it and run an entire organization.


  • A mainframe computer is an ultra-performance machine that contains higher processors and huge amounts of memory.
  • The mainframe computers are used in several places such as e-business, banking, stock exchange, and railway and airlines ticketing, research centers, telecommunications, credit card verification, insurance, finance and more.
  • Mainframe computers are designed on the principle of Reliability, Availability, and Serviceability or RAS that makes them unique.

Understanding Mainframe Computer

Mainframe Computer

Simply by the look and definition of it, a mainframe computer is a large centralized machine.

It has a much higher processing power in comparison to a standard computer due to its several high-grade processors and large memory.

Ideally, the name, ‘Mainframe’ is derived from the frame that holds the main memory and a number of processors.

Its high speed and processing power has increased its usability and importance in different sectors and fields such as:

  • Large organization
  • Consumer statistics
  • Scientific research and
  • Census data and analysis.

With its ability to carry out several complex programs simultaneously, a mainframe computer can be used as the central processing unit of several terminals and workstations connected to it.

It can not only handle thousands of Petabytes of data but, at the same time, it can also handle thousands of users in real time.

Components of Mainframe Computer

The components of the mainframe computer play a big role in ensuring a high and fast performance.

Some of the major components of a mainframe computer are:


The Central Processing Unit or CPU that comes with:

  • Different PCBs or Printed Circuits Boards
  • Processors
  • Memory modules and
  • Interfaces for every channel.

All these channels work together as a medium for communication between the memory modules and the I/O terminal with the primary objective to manage the components of the entire system and to transfer data.

Control Unit

The CU or Control Unit, also known as the bus, in the mainframe computer is linked to the storage unit area.

There are different buses in the system that have varied usage such as tapes, disks, and others.

Storage Unit

The storing unit of a mainframe computer performs a lot of different tasks such as:

  • Accessing data
  • Storing data
  • Retrieving data
  • Data insertion and
  • Saving the data.

A storage unit may have several devices such as tape drives, hard drives, punch cards, and others with a capability that is million times faster than a normal computer, all of which are controlled by the CPU.


There is a multiprocessor unit in the mainframe computer.

This means that there are several processors that help in processing the multitude of data by using interrupt handling and error handling within a very short time frame.


The motherboard of the mainframe computer comes with a number of components in it such as:

All these use the bus architecture of it to perform.

I/O Channels

There are different I/O channels in a mainframe computer system that helps in performing specific techniques such as:

  • IOCDS which stands for I/O Control Data Set
  • ESCON, which stands for Enterprise Systems Connection and
  • FICON, which stands for Fiber Connector.

Cluster Controller System

This particular device of the mainframe computer typically, comes in two different variants such as:

  • Channel attached cluster controllers and
  • Link attached cluster controllers.

The cluster controller system helps to attach the host terminal system and the channel terminal.

Functions of Mainframe Computer

A mainframe computer performs different functions that can be broadly divided into these main segments.

  • Data Warehouse System – Unlike normal computers that store data in a hard disk for longer life, the mainframe computer stores them inside it in application form. The users can access their files remotely when they try to login with the connected terminals since the mainframe computer will let all remote terminals access the files and programs stored in it.
  • Preserve Authentication Access Permission – The fact that the mainframe computer stores all data and program files in a single mainframe system, this improves productivity and efficiency. The administrators can insert data and applications into the system and also decide the number of users who can access them which prevent harmful attacks from the intruders.
  • Allot Processor Time Frame – The mainframe computer system has a very restricted number of processing time for splitting into all users who are logged in currently with the system. The system decides the types of priorities to be linked with different users with the administrator having the power to decide how the processor time should be assigned to the different types of users.
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The mainframe computer was usually designed for offering raw computational speed but the modern machines are characterized less by it and more by:

  • Redundant inner engineering which offers higher security and reliability
  • Extensive input-output services to offload to different engines
  • Backward compatibility with older software
  • Hardware hot swapping
  • High computational and hardware utilization rates via virtualization for higher throughput
  • Higher stability to run continuously for very long periods of time and
  • Lower MTBF or Mean Time Between Failures.

Most importantly, the infrastructure necessities are now reduced drastically since the 1990s as compared to the design of the earlier mainframe computers.

This is because the older bipolar technology is replaced by the Complementary Metal Oxide Semiconductor or CMOS mainframe design.

However, the Return On Investment or ROI from a mainframe computer may not be same for all computing platforms because it is dependent on different factors such as:

  • Its ability to scale
  • Its support for mixed workloads
  • The associated labor costs
  • Ability to deliver uninterrupted service and
  • The associated risks and risk-adjusted cost factors.

However, the modern mainframe computers consume less energy, need less power and cooling, which is good for the large data centers in terms of cost.

The modern mainframe computers also need less physical space.

The usual impression of the user interface of a mainframe computer of an old CRT or Cathode Ray Tube green screen monitors with 80 x 24-character is replaced, In fact, the modern mainframe computers look pretty much like a UNIX system or a personal computer.


However, there are some disadvantages of the mainframe computers, which is why these machines are not usable for any normal user.

The high cost of these systems is not affordable for any normal user.

Also, it needs a different operating environment from a normal computer that should have low temperature and large and well ventilated space.

It also needs expert professionals for its maintenance and upkeep. If one component fails, the whole system will break down, which is a major setback for these computers.

The mainframe computers use a lot of resources as compared to regular computer systems which adds to the cost.

The fact that there is more than one operating system installed in a mainframe computer increases the complexity for the users to use the system and for the system to read the instructions.

Who Uses Mainframe Computers?

What is Mainframe Computer

In spite of the disadvantages, which are mainly for the normal users, a mainframe computer is extensively used by the large scale organizations since these machines are able to carry out millions of transactions in a second.

These organizations typically need to deal with huge amounts of data every second.

And, surprisingly, even you as an individual use a mainframe computer!

Well, the Automated Teller Machine you use to draw money is an example of a mainframe computer.

The different sectors that use a mainframe computer are:

  • E-business
  • Banking
  • Finance
  • Insurance
  • Utilities
  • Government agencies and
  • It organizations

A mainframe computer can be used for all those mission-critical applications which include and are not limited to:

  • Customer order processing
  • Customer analysis
  • Financial transactions
  • Payroll computations
  • Production management
  • Inventory control
  • Large scale business accounting
  • Business transactions
  • Scientific and engineering computations and
  • Information retrieval.

Apart from that, most of the busiest websites use a mainframe host to store their magnanimous production databases.

When you access a business application through a web browser, it is often a mainframe computer that performs the vital functions behind the scenes.

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Where and Why Mainframe Computers are Used?

Some of the major sectors where a mainframe computer has proved to be an integral part in their daily operations are:

  • Health Care Sector – They can manage personalized information of all patients with utmost privacy which helps in treatments and maintaining appointment schedule
  • Defense Sector – They can pass information securely in different areas such as land, planes, ship, and home base
  • Education Sector – Big educational institutions such as international university can keep proper track of all their students, teachers, employee and documents and
  • Retail Industry – They can manage their customer base more efficiently which is huge and ever-growing and also manage their inventory, accounting and transactions with more accuracy.

In addition to the above, there are also some other areas of businesses where a mainframe computer is used to manage their huge customer database. These include and are not limited to:

  • Payroll, accounting, transactions and inventory management in businesses
  • Data and information storage and retrieval by individuals and businesses and
  • Airline and railway ticket reservation centers.

The main reason that the businesses today rely heavily on a mainframe computer are:

  • They can perform large number of transaction processing within seconds
  • They support thousands of users
  • They allow using multiple application programs at the same time by using several resources
  • They help in better management of huge amount of information in databases
  • They help the business to stay on the information superhighway
  • They can deal with communications with large bandwidth
  • They exhibit RAS or Reliability, Availability, and Serviceability characteristics
  • They allow more secure management and control of accounting data, customer lists, employee information, and others
  • They are more scalable which allows the IT infrastructure to cope with the ever increasing demand
  • Their compatibility with other devices, older software and programs
  • They offer zero downtime due to efficient offloading of work to other I/O cards and processors when required and
  • They offer a lot of other advantages.

As for the list of advantages it includes their perception of virtualization where the entire system is split into smaller logical segments to eliminate memory issues and increase performance levels.

These machines are self-serviceable which reduces the cost of maintenance by the businesses.

This means that these systems can identify the bugs and threats to it and recover from them.

Since the design of the mainframe computers is more flexible, it allows more customization to suit the requirement of every user with support provided to several operating systems at the same time.

Finally, it is the longevity, which is ideally up to 40 years, that is making the mainframe computers so favored and reliable in the business sectors today.

Types of Mainframe Computers

There are different types of mainframe computers of different brands that can be used in different sectors according to the user and computing requirements.

However, the major ones are:

  • ENIAC – A short for Electronic Numerical Integrator and Computer, the ENIAC mainframe computer was mainly developed to make the atomic bomb! There are as many as 30 separate units in this system along with one in-built air cooling system and power supply. These heavy machines, often weighing about 30 tons, have different resistors, capacitors, and components that consume excessive power to the tune of up to 2000 kilowatts.
  • UNIVAC – A short for Universal Automatic Computer, the UNIAC mainframe computer is the successor of the ENIAC mainframe computer system. These machines however had improved processing speed and a smaller size in comparison to their predecessors. These machines are known for producing accurate results.
  • ASCC – A short for Automatic Sequence Control Computer, the ASCC mainframe computer systems was developed to solve the addition and multiplication problems in quick time.

Initially, IBM or the International Business Machines was the leading mainframe computer manufacturer but over time there are others who joined the bandwagon.

Features of Mainframe Computers

Some of the useful features of the mainframe computers that have made them so popular in those sectors that deal with larger data sets are:

  • Long lasting performance – With proper maintenance and upkeep a mainframe computer can continue to offer higher and faster performance for not months but years at a stretch due to the sharing of the workload by different processors.
  • Storage – The mainframe computers come with larger storage capacity that helps the organizations to safely store and retrieve data as and when required. Also, the mainframe computers allow using virtual storage systems.
  • Centralized server – The centralized server with multiple operating systems allows better operations and management which results in higher performance, more efficiency and accuracy.
  • Time sharing – The time sharing feature allows several users to work on one single system at a time.
  • RAS – A short for Reliability, Availability, and Serviceability, this feature of the mainframe computer makes it unique from other computing systems. It allows easier data processing, scalability, and uninterrupted service.
  • Scalability – This feature makes up for the high cost of the mainframe computers since users can add to its capacity on the same system and manage the resources using the same available infrastructure.
  • Security – The data is safe in a mainframe computer because no unauthorized user is allowed to access or use it. The system is also well protected from bugs, viruses and other malware attacks. The design of the database allows it to work with total security.
  • Compatibility – The mainframe computers can work with other systems with similar applications. However, the applications are designed long back because the mainframe computers are not changed frequently. Nevertheless, as and when required, changes in the applications can be made then and there to meet the new requirements. This and the backward compatibility feature allow the users to work with operating systems and prevent their investment from going bad.
  • Throughput computing – This feature allows the mainframe computer to manage the high amount of data passing into or from the system more efficiently and easily. The centralized CPU allows it to manage the large number of servers it has to work with.
  • Fault tolerance computing – This feature ensures that the mainframe computer does not make any blunders while transferring a large amount of data in its database. This along with the massive storage and high-speed processors allows the users to have an accurate output.
  • Transactional processing – This particular characteristic of the mainframe computer allows updating the database for any type of goods. A huge amount of data can be updated in a single database with this type of processing with adequate support from the huge memory and storage capacity of the mainframe computers.
  • Multiple operating system support – The mainframe computers can manage several complex operating systems such as VMS, UNIX, along with other IBM operating systems such as Z/OS and Z/VM.
  • Tightly Coupled Clustering Technology – This feature of the mainframe computers helps them to manage around 32 systems in conjunction with a single system image. This means that if one system fails due to damage in any of the hardware components, the current job will be moved to another system that is working so that the data is not corrupted.
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However, in spite of all these useful features the terminals of the mainframe computers fail to produce a very high user experience because these systems are not designed for a typical end user.


The mainframe computers today are very useful for businesses and since you now know their utility and different types, you can easily choose a variety for your particular type of computing requirements.

Irrespective of whichever model you choose, rest assured to get a higher and faster performance.

About Puja Chatterjee

AvatarPuja Chatterjee, a distinguished technical writer, boasts an extensive and nuanced understanding of computer technology. She is an esteemed graduate of the Bengal Institute of Management Studies (BIMS), where she honed her skills and knowledge in the tech domain. Over the span of more than 12 years, Puja has developed a deep expertise that encompasses not only technology writing, where she articulates complex technical concepts with clarity and precision, but also in the realm of client relationship management. Her experience in this area is characterized by her ability to effectively communicate and engage with clients, ensuring their needs are met with the highest level of professionalism and understanding of their technical requirements. Puja's career is marked by a commitment to excellence in both written communication within the tech industry and fostering strong, productive relationships with clients.

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Puja Chatterjee
Puja Chatterjee, a distinguished technical writer, boasts an extensive and nuanced understanding of computer technology. She is an esteemed graduate of the Bengal Institute of Management Studies (BIMS), where she honed her skills and knowledge in the tech domain. Over the span of more than 12 years, Puja has developed a deep expertise that encompasses not only technology writing, where she articulates complex technical concepts with clarity and precision, but also in the realm of client relationship management. Her experience in this area is characterized by her ability to effectively communicate and engage with clients, ensuring their needs are met with the highest level of professionalism and understanding of their technical requirements. Puja's career is marked by a commitment to excellence in both written communication within the tech industry and fostering strong, productive relationships with clients.
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