Dale - Computer Science Illuminated 245

Dale - Computer Science Illuminated 245 - X) and two-part...

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218 Chapter 7 Low-Level Programming Languages We key in a number and press Continue . This screen appears twice more. If the first number we key in is 4, the second is 6, and the third is 1, we get the following output. The input is shown along with the output from the program. The first test case runs correctly. You are asked to finish implementing the test plan in the exercises. Summary A computer can store, retrieve, and process data. A user can enter data into the machine, and the machine can display data so that the user can see it. At the lowest level of abstraction, instructions to the machine directly relate to these five operations. A computer’s machine language is the set of instructions that the machine’s hardware is built to recognize and execute. Machine-language programs were written by entering a series of these instructions in their binary form. The Pep/7 is a virtual computer with two registers (A and
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Unformatted text preview: X) and two-part instructions. One part of the instruction tells what action the instruction performs, and the other part specifies the location of the data to be used (if any). Programs written using the Pep/7 instruc-tion set can be run using a simulator, a program that behaves like the Pep/7 computer. The Pep/7 assembly language is a language that allows the user to enter mnemonic codes for each instruction rather than binary numbers. Programs written in assembly language are translated into their machine-language equivalents, which are then executed using the Pep/7 simulator. Programs, like algorithms, must be tested. Code-coverage testing involves determining the input to the program by looking carefully at the programs code. Data-coverage testing involves determining the input by considering all possible input values....
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