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Evolution and History of Programming Languages Software/Hardware/System Software Programming Language History Timeline Popularity The Evolution of Programming Languages To build programs, people use languages that are similar to human language. The results are translated into machine code, which computers understand. Programming languages fall into three broad categories: • Machine languages • Assembly languages • Higher-level languages The Evolution of Programming Languages Machine Languages • Machine languages (first-generation languages) are the most basic type of computer languages, consisting of strings of numbers the computer's hardware can use. • Different types of hardware use different machine code. For example, IBM computers use different machine language than Apple computers. The Evolution of Programming Languages Assembly Languages • Assembly languages (second-generation languages) are only somewhat easier to work with than machine languages. • To create programs in assembly language, developers use cryptic English-like phrases to represent strings of numbers. • The code is then translated into object code, using a translator called an assembler. Assembly code Assembler Object code The Evolution of Programming Languages Higher-Level Languages Higher-level languages are more powerful than assembly language and allow the programmer to work in a more English-like environment. Higher-level programming languages are divided into three "generations," each more powerful than the last: • Third-generation languages • Fourth-generation languages • Fifth-generation languages Higher-Level Languages Third-Generation Languages • Third-generation languages (3GLs) are the first to use true English-like phrasing, making them easier to use than previous languages. • 3GLs are portable, meaning the object code created for one type of system can be translated for use on a different type of system. • The following languages are 3GLs: FORTRAN COBOL BASIC Pascal C C++ Java ActiveX A Typical C Program Development Environment • Phases of C Programs: Editor Disk Preprocessor Disk Compiler Disk Linker Disk 1. Program is created in the editor and stored on disk 2. Preprocessor program processes the code 3. Compiler creates object code and stores it on disk. 4. Linker links the object code with the libraries 2. Preprocess 3. Compile 4. Link 5. Load Primary Memory Loader 5. Loader puts program in memory. Disk Primary Memory CPU 1. Edit 6. CPU takes each instruction and executes it, possibly storing new data values as the program executes 6. Execute Higher-Level Languages Fourth-Generation Languages • Fourth-generation languages (4GLs) are even easier to use than 3GLs. • 4GLs may use a text-based environment (like a 3GL) or may allow the programmer to work in a visual environment, using graphical tools. • The following languages are 4GLs: Visual Basic (VB) VisualAge Authoring environments Higher-Level Languages Fifth-Generation Languages • Fifth-generation languages (5GLs) are an issue of debate in the programming community – some programmers cannot agree that they even exist. • These high-level languages would use artificial intelligence to create software, making 5GLs extremely difficult to develop. • Solve problems using constraints rather than algorithms, used in Artificial Intelligence Summary Hardware Description Language HDL HDL What and why HDL?? Hardware Description Language Basic idea is a programming language to describe hardware Initial purpose was to allow abstract design and simulation Design could be verified then implemented in hardware Now Synthesis tools allow direct implementation from HDL code. Large improvement in designer productivity HDL HDL allows write-run-debug cycle for hardware development. Similar to programming software Much, much faster than design-implementdebug Combined with modern Field Programmable Gate Array chips large complex circuits (>100000s of gates) can be implemented. HDLs There are many different HDLs VHDL is the most common Verilog HDL ABEL VHDL Large standard developed by US DoD VHDL = VHSIC HDL VHSIC = Very High Speed Integrated Circuit Verilog HDL is second most common Easier to use in many ways = better for teaching C - like syntax Verilog HDL Verilog constructs are use defined keywords Examples: and, or, wire, input output One important construct is the module Modules have inputs and outputs Modules can be built up of Verilog primatives or of user defined submodules. Example: Simple Circuit HDL module smpl_circuit(A,B,C,x,y); input A,B,C; output x,y; wire e; and g1(e,A,B); not g2(y, C); or g3(x,e,y); endmodule HDL Summary Hardware Description Languages allow fast design and verification of digital circuits. Accurate simulation and testing requires delays and inputs to be specified. There are three different levels of abstraction for modelling circuits. System Design Language Hardware and Software Co-design What is Codesign? Why Codesign (1) ? Why Codesign (2) ? Traditional Design Flow 27 HW/SW Codesign Flow Concurrent design between hardware and software using Co-simulation Co-synthesis 28 Codesign Language Software Description Language (SDL) People know C, so how about languages built on C/C++? SystemC SpecC Handel-C Hardware Description Language (HDL) Has no tool support. Only useful for influencing other languages. Lacks CAD tool support Proprietary: Not universally available SystemC History VSIA SLD Data Types Spec (draft) Synopsys Synopsys ATG “Scenic” UC Irvine SystemC v0.90 Sep. 99 Synopsys “Fridge” 1996 Frontier Design A/RT Library Fixed Point Types SystemC v1.0 Apr. 00 1991 imec 1992 CoWare “N2C” 1997 Abstract Protocols SystemC v1.1 Jun. 00 SystemC Highlights Features as a codesign language Modules Processes Ports Signals Rich set of port and signal types Rich set of data types Clocks Cycle-based simulation Multiple abstraction levels Communication protocols Debugging support Waveform tracing Current System Design Methodology C/C++ System Level Model Refine Manual Conversion Analysis Results Problems Errors in manual conversion from C to HDL Disconnect between system model and HDL model Multiple system tests VHDL/Verilog Simulation Synthesis Rest of Process Summary&Questions Software/Hardware/System Design Languages