Encyclopedia of Computer Science and Technology

392 punched cards and paper tapepunched cards and paper tapeIn 1804, the French inventor Joseph-Marie Jacquardinvented an automatic weaving loom that used a chain ofpunched cards to control the pattern in the fabric. A generationlater, a British inventor (see Babbage, Charles)decided that punched cards would be a suitable medium forinputting data into his proposed mechanical computer, theAnalytical Engine.Although Babbage’s machine was never built, by 1890an American inventor was using an electromechanical tabulatingmachine to process census data punched into cards(see Hollerith, Herman). Card tabulating machines wereimproved and marketed by International Business Machines(IBM) throughout the first part of the 20th century. IBMwould also create the 80-column standard punched cardthat would become familiar to a generation of programmers.Later machines included features such as mechanicalsorting, enhanced arithmetic functions, and the ability togroup cards by a particular criterion and print subtotals,counts, or other information about each group. Althoughthese machines were not computers, they did introduce theidea of automated data processing.During the 1930s, a number of companies introducedpunch card tabulators that could work with alphanumericdata (that is, letters as well as numbers). With theseexpanded capabilities, punch card systems could be usedto keep track of military recruits, taxpayers, or customers(such as insurance policy holders). IBM emphasizedthe new machines’ features by calling them “accountingmachines” instead of tabulators.While tabulators and calculators using punched cardsgave a taste of the power of automated data processing,they had a very limited programming ability. For example,they could not make more than very simple comparisons ordecisions, and could not repeat steps under program control(looping). The desire to create a general-purpose dataprocessing system led in the 1940s to the development ofthe electronic computer.When the first computers were developed, it was naturalto turn to the existing punched cards and their machineryfor a medium for inputting data and program instructionsinto the new machines. Because computers contained workingmemory, the program could be stored in its entiretyduring processing, enabling looping, subroutines, and otherways to control processing. Because the amount of availablememory or “core” was severely limited, not much datacould be stored inside the computer. However, complicatedprocessing could be broken into a series of steps where aprogram was loaded and run, the input data cards read andprocessed, and the intermediate results punched onto a setof output cards. The card could then be input to anotherprogram to carry out the next phase.By the 1970s, however, faster and easier to use mediasuch as magnetic tape and disk drives were being employedfor program and data storage. Instead of having to use akeypunch machine to create each program statement, programmerscould type their commands at a terminal, usinga text editor (see programming environment). Even thegovernment began to phase out punched cards. Today some“legacy” punch card systems are maintained, and thereis sometimes a need to read and convert archival data inpunch card form.Ironically, this workhorse of early data processingwould surface again in the U.S. presidential election of2000, when problems with the interpretation of partlypunched “chads” on ballot punch cards would lead togreat controversy.Further ReadingCardamation Company. Available online. URL: http://www.cardamation.com/.Accessed August 17, 2007.Dyson, George. “The Undead: The Little Secret That Haunts CorporateAmerica: A Technology That Won’t Go Away.” Wired7.03 (March 1999): 141–145, 170–172. Available online. URL:http://www.wired.com/wired/archive/7.03/punchcards.html.Accessed August 17, 2007.Philips, N. V. “Everything About Punch Cards.” Available online. URL:http://www.museumwaalsdorp.nl/computer/en/punchcards.html. Accessed August 17, 2007.Province, Charles M. “IBM Punch Cards in the Army.” Availableonline. URL: http://www.geocities.com/pattonhq/ibm.html.Accessed February 9, 2008.PythonCreated by Guido van Rossum and first released in 1990,Python is a relatively simple but powerful scripting language(see scripting languages and Perl). The namecomes from the well-known British comedy group MontyPython.Python is particularly useful for system administrators,webmasters, and other people who have to link variousfiles, data source, or programs to perform their daily tasks.The language currently has a small but growing (and quiteenthusiastic) following.Python dispenses with much of the traditional syntaxused in the C family of languages. For example, the followinglittle program converts a Fahrenheit temperature to itsCelsius equivalent:temp = input(“Farenheit temperature:”)print (temp-32.0) *5.0/9.0Without the semicolons and braces found in C andrelated languages, Python looks rather like BASIC. Alsonote that the type of input data doesn’t have to be declared.The runtime mechanism will assume it’s numeric from theexpression found in the print statement. Python programsthus tend to be shorter and simpler than C, Java, or evenPerl programs. The simple syntax and lack of data typingdoes not mean that Python is not a “serious” language,however. Python contains full facilities for object-orientedprogramming, for example.Python programs can be written quickly and easily bytrying commands out interactively and then converted thescript to bytecode, a machine-independent representationthat can be run on an interpreter designed for each machineenvironment. Alternatively, there are translation programsthat can convert a Python script to a C source file that canthen be compiled for top speed.