The Internet Phenomenon - Secure Java: For Web Application Development - page 4

and afordable to a very few—governments, top educational and research institutions, and a few
large enterprises. he architecture of these mainframes was simple, single-tiered, and mammoth
in size and demanded sizable infrastructure real estate space requirements for installation and
connectivity with other systems.
A mainframe computer was connected to many input/output (I/O) units and peripherals.
Initial mainframe systems came with card/tape reader peripherals and printers as the I/O units
for the systems. Programmers needed to create programs by punching cards, each single line
of the program on a per card basis, and submit the program for compilation and running by
submitting the set of cards in a proper sequence to the card readers. Once the program was
compiled, it could be submitted for processing as a “batch job.” Once the batch job was queued
for execution, the output from the program was usually collected as a text/numerical format-
ted printout.
Introduction of text-based terminals, sometimes referred to as dumb terminals today, improved
the I/O interactivity with the mainframe systems. However, these terminals simply acted as con-
duits for communication between the user and the mainframe's processing system. he output
from the mainframe was sent back to these terminals in the form of text or numerical format.
he architecture of such systems was referred to as a centralized model . As the technology pro-
gressed during this era, newer peripherals, such as spooled tapes and other magnetic media, started
improving the user friendliness of the mainframe system. A typical mainframe architecture would
have been as simple as the one depicted in Figure 1.1.
A mainframe system consisted of a core processing unit with a main memory for processing
purposes and a secondary memory unit to store the programs or applications from the users. he
terminals were hardwired to the mainframe systems and, therefore, were bound by several limiting
factors with regard to scalability and expandability of the mainframe systems.
On the utility aspects of the mainframe, the vendors used to provide a set of built-in pro-
gram libraries called subroutines , which could be appropriately used by the programmer for stan-
dard business/scientiic applications. While scientiic-based application programs used advanced
mathematical subroutines for scientiic computations, business-oriented programs used basic

Te rminals

Mainframe

Figure 1.1 Mainframe architecture.