87 Programming James M. Feldman 87.1 Assembly Language Edward W. czeck Numbercount().comparisOnsDownontheFactory Floor.compilerOptimizationandASsemblyLanguage 87.2 High-Level Languages Ted G. Lewis What Is a HLL?. How High Is a HLL?. HLLs and Paradigms 87.3 Data Types and Data Structures Abstract Data Types. Fundamental Data Types. Type Johannes J Martin Constructors. Dynamic Types. More Dynamic Data University of New Orleans Types.Object-Oriented Programming 87.1 Assembly Language James M. Feldman and Edward W. Czeck The true language of computers is a stream of Is and Os-bits. Everything in the computer, be it numbers or text or program, spreadsheet or database or 3-D rendering, is nothing but an array of bits. The meaning of the bits is in the"eye of the beholder; it is determined entirely by context. Bits are not a useful medium for human consumption. Instead, we insist that what we read be formatted spatially and presented in a modest range of isually distinguishable characters. 0 and 1 arranged in a dense, page-filling array do not fulfill these require- ments in any way. The several languages that are presented in this handbook are all intended to make something readable to two quite different readers On the one hand, they serve the human reader with his/her requirements on symbols and layout; on the other, they provide a grammatically regular language for interpretation by a mpiler. A compiler, of course, is normally a program running on a computer, but human beings can and sometimes do play both sides of this game. They want to play with both the input and output. Such accessibility requires that not only the input but the output of the compilation process be comfortably readable by humans The language of the input is called a high-level language(HLL). Examples are C, Pascal, Ada and Modula II They are designed to express both regularly and concisely the kinds of operations and the kinds of constructs that programmers manipulate The output end of the compiler generates object code-a generally unreadable, binary representation of machine language, lacking only the services of a linker to turn it into true machine language. The language that has been constructed to represent object code for human consumption is assembly language. That is the subject of this section. Some might object to our statement of purpose for assembly language. While few will contest the concept of assembly language as the readable form of object code, some see writing assembly code as the way to"get their hands on the inner workings of the machine. They see it as a"control"issue. Since most HLLs today give the user reasonably direct ways to access hardware, where does the"control"issue arise? What assembly proponents see as the essential reason for having an assembly language is the option to optimize the"important sections of a program by doing a better job of machine code generation than the compiler does. This perspective was valid enough when compilers were mediocre optimizers. It was not unlike the old days when a car came with a complete set of tools because you needed them. The same thing that has happened to cars has happened to compilers. They are engineered to be"fuel efficient "and perform their assigned functions with remarkable c 2000 by CRC Press LLC© 2000 by CRC Press LLC 87 Programming 87.1 Assembly Language NumberCount( ) • Comparisons Down on the Factory Floor • Compiler Optimization and Assembly Language 87.2 High-Level Languages What Is a HLL? • How High Is a HLL? • HLLs and Paradigms 87.3 Data Types and Data Structures Abstract Data Types • Fundamental Data Types • Type Constructors • Dynamic Types • More Dynamic Data Types • Object-Oriented Programming 87.1 Assembly Language James M. Feldman and Edward W. Czeck The true language of computers is a stream of 1s and 0s—bits. Everything in the computer, be it numbers or text or program, spreadsheet or database or 3-D rendering, is nothing but an array of bits. The meaning of the bits is in the “eye of the beholder”; it is determined entirely by context. Bits are not a useful medium for human consumption. Instead, we insist that what we read be formatted spatially and presented in a modest range of visually distinguishable characters. 0 and 1 arranged in a dense, page-filling array do not fulfill these require￾ments in any way. The several languages that are presented in this handbook are all intended to make something readable to two quite different readers. On the one hand, they serve the human reader with his/her requirements on symbols and layout; on the other, they provide a grammatically regular language for interpretation by a compiler. A compiler, of course, is normally a program running on a computer, but human beings can and sometimes do play both sides of this game. They want to play with both the input and output. Such accessibility requires that not only the input but the output of the compilation process be comfortably readable by humans. The language of the input is called a high-level language (HLL). Examples are C, Pascal, Ada and Modula II. They are designed to express both regularly and concisely the kinds of operations and the kinds of constructs that programmers manipulate. The output end of the compiler generates object code—a generally unreadable, binary representation of machine language, lacking only the services of a linker to turn it into true machine language. The language that has been constructed to represent object code for human consumption is assembly language. That is the subject of this section. Some might object to our statement of purpose for assembly language. While few will contest the concept of assembly language as the readable form of object code, some see writing assembly code as the way to “get their hands on the inner workings of the machine.” They see it as a “control” issue. Since most HLLs today give the user reasonably direct ways to access hardware, where does the “control” issue arise? What assembly proponents see as the essential reason for having an assembly language is the option to optimize the “important” sections of a program by doing a better job of machine code generation than the compiler does. This perspective was valid enough when compilers were mediocre optimizers. It was not unlike the old days when a car came with a complete set of tools because you needed them. The same thing that has happened to cars has happened to compilers. They are engineered to be “fuel efficient” and perform their assigned functions with remarkable James M. Feldman Northeastern University Edward W. Czeck Northeastern University Ted G. Lewis Navel Postgraduate School Johannes J. Martin University of New Orleans