1 Lecture 1 Getting ready to program Hardware Model Software Model Programming Languages The C Language Software Engineering Programming.
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1 Lecture 1 Getting ready to program Hardware Model Software Model Programming Languages The C Language Software Engineering Programming Environment Readings: Chapter 1 Section 1
2 Hardware Model The physical machines that make up a computer installation: Secondary Storage Input Devices Output Devices CPU Main Memory
3 Hardware: CPU Acronym for … The “ brain ” of computer Consists of a processing unit (the ALU), a control unit (the CU) and a set of registers (a few high- speed memory units for temporary use) Fetch and execute instructions from the main memory until the computer is turned off ALU CU Register File CPU
4 Hardware: Main Memory The place for storing data of all kinds Bit (Binary Digit, smallest unit) stores either 0 or 1 Byte - consists of 8 bits Main memory a list of bytes, each associated with an address stores both the program and data e.g. 64K bytes of memory: 0 1 2 65535............
5 Software Model Software A collection of programs for a specific task e.g. operating system (OS), editor, compiler, game, database server Operating System Chief servant, managing tasks and resources allocates the computer ’ s resources to the different tasks that the computer must accomplish What are the most popular OS ’ s? e.g. DOS, Windows, UNIX, Solaris, Linux, etc.
6 Editor C Compiler Pascal Compiler Games Web Browser System and Application Software Hardware-Software Hierarchy Operating System Hardware
8 Software: Program & Data Program - a sequence of instructions specifying how the data is to be processed. Data - input to the program, either supplied during runtime or pre-stored in the computer Both program and pre-stored data are stored in the main memory Originally, in secondary storage, e.g., CD or hard disk, before loaded into the main memory
9 Programming Languages (PL) Can You Understand This? Is This Better?
10 PL: Machine Languages A CPU only understands its own machine language => portability problem In Motorola 68000, the following 4 bytes is an instruction to move the value in register D3 to memory address 104. In Intel 80486, the same sequence of bytes represents different instructions Coding is tedious and error prone 192 49 104 0
11 PL: Assembly Languages Use English-like abbreviations e.g. the previous MC68000 machine instruction is written as: MOVE D3, 104 slightly easier for human to understand need an assembler to translate into machine instructions Different CPUs have different instruction sets e.g. MOVE D3, 104 is not a valid instruction in Intel 80486 because it doesn ’ t even have a register called D3 => portability problem
12 PL: High-level Languages Close(r) to human language One single statement accomplishes substantial tasks Need a compiler/linker to translate into machine language More portable - the same program (more or less) works for different machines e.g. Fortran, COBOL, Pascal, Ada, Modula, C, C++, Lisp, Prolog, Java, Perl...
13 PL: Compiler & Linker Compiler translates a program in high- level language into an object program (or object code). The original program is called the source program/code. Linker combines the object code of a program with other pre- compiled object codes to generate an executable code which is in machine language linker compiler source code object code other object code executable code
14 The C Language Developed by Dennis Ritchie in 1970 ’ s Originally for writing system programs such as OS (e.g. UNIX) and compilers Efficient and widely used in engineering applications Small and easy to get started easy to make undetected errors
15 C: Standardization & Libraries ANSI/ISO Standard for C: 1990 C Standard Libraries Contains pre-written functions Greatly facilitates programming and performance Generally provided by compiler vendors Proprietary libraries provided by individual vendors
16 Software Engineering Start Problem definition Algorithm design Desktop testing Problem-solving phase Translating to C Testing Working program Implementation phase
17 SE: Development Process Specify the task Find an algorithm for its solution Code the algorithm in a programming language Prepare the source code (program) in a file, called source file Test the code Compile the source file to produce object code, stored in an object file Link up the object code with any library module and load the loader to produce the final executable file Run the executable file and debug any error
18 SE: Development Process No complete set of rule! Split a BIG problem into few smaller problems Solve the smaller problems one by one Combine the solutions of smaller problems Strategy –Top-down design –Stepwise refinement
19 Programming Environment Editor Disk Preprocessor Disk Compiler Disk Linker Disk
20 Programming Environment............ Loader CPU Disk Main Memory
21 Programming Errors Syntax errors: violation of the syntax detected during compilation Run-time errors: compilation successful but errors detected during run- time, e.g. division by zero Logic error: compilation and execution do not produce machine detectable errors but the answer is wrong may be due to wrong algorithm or wrong coding
22 Tips for A Good Programmer Not only know how to write a program, but also know how to write a good program Writing a program may be simple, but writing a program with unique and good programming styles is not simple