QuoteRef: wilkMV_1951

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history of computers
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separate a module's interface specification from its implementation
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debugging techniques
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function library
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source-rich system
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exceptions and undesired events
people vs. computers
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logging data and events
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testing by voting or N-version
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Wilkes, M.V., Wheeler, D.J., Gill, S., "Preparation of programs for an electronic digital computer, with special reference to the EDSAC and the use of a library of subroutines", Reading, Massachusetts, Addison-Wesley, 1951. Google

Other Reference

reprinted Charles Babbage Institute reprint series for the history of computing, vol 1, Los Angeles: Tomash Publishers 1982 with an introduction by M. Campbell-Kelly


published from a report dated September 1950

ix ;;Quote: brief history of the development of the EDSAC by Wilkes and others; 1946-1949
xiv ;;Quote: a Japanese computer, the TAC, used the same order codes and subroutine library as the EDSAC; only source was this book
xxi ;;Quote: the EDSAC subroutine library included the Runge-Kutta-Gill process for solving differential equations
xxii ;;Quote: Wilkes preferred print orders and post-mortem routines over "peeping", i.e., observing a program's progress through a CRT monitor
xxiv ;;Quote: scaling was the most difficult part of programming the EDSAC
xxv ;;Quote: the EDSAC book includes code for the principal library subroutines. It served as a model for early programmers
xxvi ;;Quote: can simulate the EDSAC and its subroutine library from the book
1 ;;Quote: a program is a sequence of orders for performing a calculation; unlike a human, every contingency must be foreseen
1+;;Quote: a computer can perform only the basic operations of arithmetic
1 ;;Quote: with a computer, the simplest mathematical calculation requires an extended sequence of orders
1+;;Quote: use subroutines to reduce the labor of writing a program; i.e., short, ready-made programs
1+;;Quote: it is worth-while to spend much effort on the establishment of a subroutine library and a system for combining subroutines into a program
3 ;;Quote: use the same memory for both orders and numbers by expressing orders in a numerical code; from von Neumann's report
3+;;Quote: a computer consists of memory, an arithmetical unit, input and output mechanisms, and a control unit
3 ;;Quote: the EDSAC used 1024 numbers of ultrasonic memory; 17 or 35 binary digits from -1 to 1
3+;;Quote: the address of x is the reference number of the storage location holding x
5 ;;Quote: EDSAC code used 18 orders indicated by letters with an address and length flag
9 ;;Quote: construct a program with many fewer orders by modifying the orders during program execution
15 ;;Quote: the EDSAC initial orders converted symbolic orders to binary form and loaded them into memory; reduces error; 41 words
17 ;;Quote: use "control combinations" to direct EDSAC's initial orders
19 ;;Quote: use relocatable code for library subroutines; allows mechanical copying of subroutines
22 ;;Quote: an open subroutine is copied as is to a program; a closed subroutine is called from the master routine with a Wheeler jump
23 ;;Quote: a preset parameter is evaluated at load time; a program parameter is placed immediately after the subroutine call
25 ;;Quote: for each subroutine, EDSAC's library catalog gave a concise specification, operating time, storage space, and the orders in full
27 ;;Quote: the assembly subroutine combined a master routine with subroutines, generated subroutine calls, and resolved input data; seldom used
34 ;;Quote: EDSAC include interpretive routines for complex numbers and floating point arithmetic; they coined the term
35 ;;Quote: an interpretive routine extends the order code of the machine at the cost of greater execution time
38 ;;Quote: it is easy to make expensive programming errors; the EDSAC group developed techniques to avoid or detect errors before execution and to locate errors after execution
38 ;;Quote: test subroutines with short programs constructed for the purpose
38 ;;Quote: avoid and detect errors by orderly and logical programs; rewrite if necessary and provide documentation
38+;;Quote: the EDSAC group did not use flowcharts
38 ;;Quote: use desk checking to verify that subroutines occupy distinct locations, specifications are satisfied, overwrites do not occur, and unpreserved registers are invalid
39 ;;Quote: use a post-mortem program to print the contents of store after an error or infinite loop
39 ;;Quote: trace program execution by printing a letter when each subroutine executes
40 ;;Quote: check a program by interpreting the program instead of executing it directly; print additional information
40 ;;Quote: a blocking order transfers control from a program to the checking routine
41 ;;Quote: debug a program by printing intermediate results; include extra printing with the first draft
41 ;;Quote: subroutines for the assembly of repetitive programs; like structured programming, but seldom used
42 ;;Quote: users punched their own tape and hanged the tape with a ticket on a horizontal wire; the operator processed the tapes in order
43 ;;Quote: punch input data, master routine, and subroutines separately; each tape punched twice and compared to catch errors
166 ;;Quote: reduce the number of orders by using tags instead of counting; e.g., use -1 to end a sequence of positive numbers
167 ;;Quote: use a multiway switch to select a route with a number

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