Brief History of Computers and Computer Languages

CSCE1062 Outline A brief history of computers {section 1.1} Programming languages {section 1.3} Processing a high-level language program {section 1.4} Professional ethics for computer programmers {section 1.7}

CSCE1063 Early Computers First computer invented in the late 1930s to perform mathematical computations. ENIAC, the first large-scale, general purpose electronic digital computer, which was completed in 1946, used to be programmed by connecting hundreds of wires and arranging thousands of switches in a certain way. (Weighed 30 tons & occupied 9x15m 2 ). Dr. John Von Neumann, at Princeton University, in the same year proposed the concept of a stored program computer, and he designed a computer based on this idea. Stored-program computer (Von Neumann architecture) is the basis of today's digital computers.

CSCE1064 Microprocessor  Much smaller  Much more powerful Figure 1-2 The ENIAC computer (courtesy of U.S. Army Historic Computer Images) Figure 1-3 A lab technician holds a modern microprocessor (photo courtesy of Intel Corporation) Early Computers (cont’d) Source: Gaddis T. Starting Out With Games and Graphics in C++. Addison Wesley, 2010.

CSCE1065 Categories of Computers Microcomputers. Minicomputers. Mainframes. Supercomputers. Time Sharing (allowing simultaneous access to a single computer’s resources by a number of users)

CSCE1066 Programming Languages Machine Language (low-level language)  “Native tongue” of the computer  Binary 0s and 1s that specify what to do Assembly Language: Symbolic encoding of Machine Language: MVI B, 05H LDA 1234H ADD B High-Level Languages  Resemble human language (C++, C, Pascal, Java) a = a + b; Assembler Compiler

CSCE1067 Editor used to enter the program  Source program (file.cpp)  UNIX vi text editor Compiler translates the source program, producing object program (file.obj)  Displays syntax errors (not descriptive) Linker combines object file with other object files  Executable program (file.exe) Loader copies executable instructions to memory, and directs CPU to begin execution with the first instruction. Processing a High-Level Language Program

CSCE1068 Program Processing Diagram (1)

CSCE1069 Program Processing Diagram (2)

CSCE10610 Processing a High-Level Language Program (cont’d) An IDE (integrated development environment) is a package that combines a simple editor with a compiler, linker, and loader. IDEs give the developer menus from which to select steps, and if the developer tries a step that is out of sequence, the IDE simply fills in the missing steps automatically. IDEs might simply leave the program in memory; therefore, users must remember to save the source file to disk after every modification before attempting to run the program, to avoid loosing it in case something goes wrong. Examples:  C++ Builder, Microsoft Visual C++

CSCE10611 Professional Ethics for Computer Programmers Privacy and misuse of data Computer hacking Plagiarism and software piracy Misuse of a computer resource

CSCE10612 Privacy and Misuse of Data As part of their jobs, programmers may have access to large data containing sensitive/secret information. Programmers should not misuse information, just as doctors and lawyers. Computer theft/fraud is changing financial information, and could lead to fines and imprisonment.

CSCE10613 Computer Hacking Computer hackers break into secure/classified/confidential data banks by using their own computers. Computer hacking is illegal. Hackers also sometimes attach harmful code, virus, to another program so that it copies itself to a computer’s disk. Viruses spread from one infected computer to another by copying files or s.

CSCE10614 Plagiarism and Software Piracy Plagiarism, e.g. modifying another student’s code and submitting it as your own, is fraudulent. Software piracy is the practice of illegally copying software. Copying/Using someone else’s programs without permission could lead to lawsuit. Most commercial software packages are protected by copyright laws against software piracy. It is important to read the copyright restrictions on each software package and adhere to them.

CSCE10615 Misuse of a Computer Resource As computer technology spreads throughout modern society, so do the opportunities for its misuse. Computers, computer programs, data and accounts are like any other property. If they belong to someone else and you are not explicitly given permission to use them, then don’t use them. Computer access privileges or user account codes are private property which are usually granted for a specific purpose.