158 COMPUTER HARDWARE, SOFTWARE
- Input and output (I/O) devices to communicate with other computers or
devices - Buses that provide communication between various computer
elements
Computers all contain read - only memory whose contents are permanent —
that is, can only be read and not written to by the user, along with random
access memory that can both be read from and written to by the user. The
basic computing unit is a bit (b), which stands for binary digit; 8 bits comprise
a byte (B). Table 4.1 illustrates calculation of computer memory bytes — that
is, the number of locations that can be addressed.
Computer storage capacities are constantly increasing to keep pace with
requirements for data storage and manipulation; however, a recent model
desktop or laptop computer will have 250 gigabytes (GB) of storage capability
or more. Microcomputers, familiar to all as PC and Macintosh desktop or
laptop computers, are the basic interface for many instrumental methods
including all types of chromatography (LC, HPLC, GC), hyphenated methods
(GC – MS, LC – IR), fl ame emission spectroscopy, and basic ultraviolet – visible
and infrared spectroscopy. Microcomputers have operating systems (OS) such
as Windows and Unix or Linux variants for the PC or have Mac OS X, Linux,
and BSD (Berkeley Software Distribution or Berkeley Unix) for Apple
Macintosh computers.
Many instrument manufacturers will have individualized dedicated operat-
ing systems, based on Windows, Unix, Linux, or Sun systems that interface with
their instrumentation. Computer and instrument operators should become
familiar with more than one OS and expect them to continually undergo
change and upgrading. Microcomputers capable of performing the various
analog - to - digital or digital - to - analog conversions, ADC or DAC respectively,
in addition to PIO (parallel input output) functions are normally purchased
as an integral part of the analytical instrument in question. Upgrades to soft-
ware are to be expected during the instrument ’ s lifetime, usually requiring
hardware upgrades as well. Many molecular design, molecular modeling, visu-
alization, and computational programs will run on high - end microcomputers
as discussed in Sections 4.3 and 4.4.
Workstations, a step up in capability and cost from microcomputers, usually
feature a multitasking operating system (OS) enabling the computer to run
TABLE 4.1 Computing Units
Power of 10 Number and Unit Number of Locations (bytes)
2 10 1024 = 1 kilobyte 1024
2 20 1024 k = 1 M (megabyte) 1,048,576 (1.045 × 10^6 )
2 30 1024 M = 1 G (gigabyte) 1,073,741,824 (1.07 × 10^9 )
2 40 1024 G = 1 T (terabyte) (1.099511628 × 10^12 )