Machine languages Assembly languages Higher-level 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: The Evolution of Programming 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 - Machine 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. The Evolution of Programming Languages - Assembly Languages
Third-generation languages Fourth-generation languages Fifth-generation 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: The Evolution of Programming Languages - Higher-Level Languages
FORTANC COBOLC++ BASICJava PascalActiveX 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: Higher-Level Languages - Third-Generation Languages
A Typical C Program Development Environment 1.Edit 2.Preprocess 3.Compile 4.Link 5.Load 6.Execute Disk Loader Linker Compiler Preprocessor Editor Disk Primary Memory CPU Primary Memory 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. 5.Loader puts program in memory. 4. Linker links the object code with the libraries 6.CPU takes each instruction and executes it, possibly storing new data values as the program executes Phases of C Programs:
Visual Basic (VB) VisualAge Authoring environments 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: Higher-Level Languages - Fourth-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 Prolog Higher-Level Languages - Fifth-Generation Languages
Hardware Description Language (HDL) 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-implement- debug Combined with modern Field Programmable Gate Array chips large complex circuits (>100000s of gates) can be implemented.
HDLs There are many different HDLs Verilog HDL ABEL VHDL VHDL is the most common 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
27 HW/SW Codesign Flow Concurrent design between hardware and software using Co-simulation Co-synthesis
Codesign Language Hardware Description Language (HDL) Software Description Language (SDL) People know C, so how about languages built on C/C++? SystemC SpecC Handel-C Has no tool support. Only useful for influencing other languages. Lacks CAD tool support Proprietary: Not universally available
SystemC Highlights 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 Features as a codesign language
Current System Design Methodology C/C++ System Level Model Analysis Results Refine VHDL/Verilog Manual Conversion Simulation Synthesis Rest of Process Problems Errors in manual conversion from C to HDL Disconnect between system model and HDL model Multiple system tests