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Programming HSPM J713 Programming languages and systems

Programming languages generally come with programming system. The language part of a programming language is the key words, symbols, and syntax used to write code. ...

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Programming HSPM J713 Programming languages and systems

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  1. Programming HSPM J713

  2. Programming languages and systems • Programming languages generally come with programming system • The language part of a programming language is the key words, symbols, and syntax used to write code. • The system part translates the written code into machine instructions that computer executes. Can be a compiler or an interpreter.

  3. Platform-specific • Language system works with specific hardware • The “IBM-compatible” PC or the Windows PC • All use the same: • Machine instructions (which depends on chip architecture) • Memory, screen

  4. Assembly language mov ax, 1234h mov bx, ax Directly translates into machine code (binary numbers) Compiler translates all instructions in program into machine code Low level – explicitly manipulates registers (places to hold data) on the CPU chip. Each chip has its own assembly language

  5. FORTRAN Do 10 j = 2 , 1000 B(j) = A(j-1) A(j-1)=j 10 continue Compiled into machine language and then run Used on mainframes since 1950’s. Designed for math

  6. BASIC Beginner's All-purpose Symbolic Instruction Code For students and general users Interpreted – One line at a time is translated into machine code and executed

  7. BASIC – unstructured, interpreted 10 INPUT "What is your name: ", U$ 20 PRINT "Hello "; U$ 30 INPUT "How many stars do you want: ", N 40 S$ = "" 50 FOR I = 1 TO N 60 S$ = S$ + "*" 70 NEXT I 80 PRINT S$ 90 INPUT "Do you want more stars? ", A$ 100 IF LEN(A$) = 0 THEN 90 110 A$ = LEFT$(A$, 1) 120 IF A$ = "Y" OR A$ = "y" THEN 30 130 PRINT "Goodbye ";U$ 140 END

  8. BASIC structured, compiled INPUT "What is your name: ", UserName$ PRINT "Hello "; UserName$ DO INPUT "How many stars do you want: ", NumStars Stars$ = STRING$(NumStars, "*") PRINT Stars$ DO INPUT "Do you want more stars? ", Answer$ LOOP UNTIL Answer$ <> "" Answer$ = LEFT$(Answer$, 1) LOOP WHILE UCASE$(Answer$) = "Y" PRINT "Goodbye "; UserName$

  9. C, C++ • This Hello world program uses the C++ standard library stream facility to write a message to standard output: #include <iostream> // provides std::cout int main() { std::cout << "Hello, world!\n"; } Uses “library” of code, callable with key words, to execute complex tasks Compiler for specific platform translates that into machine code.

  10. Java • Compiled code runs on Virtual Machine • A virtual machine is written for each platform. • The virtual machine for a platform translates virtual machine instructions into machine instructions for that platform • Java runs on PC virtual machine on PC’s, Macintosh virtual machine on Macs, for example. • So compiled Java code can run on many platforms. Good for web applications.

  11. Java resembles C in syntax Class HelloWorld { public static void main (String[] arguments) { System.out.println(“Hello World!”); } } Compiled using Java Development Kit

  12. Java uses objects import java.applet.*; import java.awt.*; public class TextEntry extends Applet { TextField Reply; TextField Entry; public void init() { setBackground(Color.white); add("EntryLabel", new Label("Type your number in the small box and press Enter:")); add("Entry", Entry = new TextField("", 5)); add("Reply", Reply = new TextField("My reply will appear here.", 60)); Reply.setEditable(false); } public void compute() { int value; try { value = Integer.valueOf(Entry.getText().trim()).intValue(); if (value == 15) { Reply.setText("Correct! 15 is right!"); } else { if (value > 15) Reply.setText(Entry.getText()+" is too high."); if (value < 15) Reply.setText(Entry.getText()+" is too low."); } } catch(NumberFormatException e) { Reply.setText(Entry.getText() + " is not a number."); } } public boolean action(Event e, Object dummy) { compute(); return(true); } } Textentry example

  13. Java uses objects import java.applet.*; import java.awt.*; public class TextEntry extends Applet { TextField Reply; TextField Entry; … }

  14. Java uses objects … public class TextEntry extends Applet { TextField Reply; TextField Entry; public void init() { setBackground(Color.white); add("EntryLabel", new Label("Type your number in the small box and press Enter:")); add("Entry", Entry = new TextField("", 5)); add("Reply", Reply = new TextField("My reply will appear here.", 60)); Reply.setEditable(false); } … }

  15. Java uses objects … public void compute() { int value; try { value = Integer.valueOf(Entry.getText().trim()).intValue(); if (value == 15) { Reply.setText("Correct! 15 is right!"); } else { if (value > 15) Reply.setText(Entry.getText()+" is too high."); if (value < 15) Reply.setText(Entry.getText()+" is too low."); } } catch(NumberFormatException e) { Reply.setText(Entry.getText() + " is not a number.");} } public boolean action(Event e, Object dummy) { compute(); return(true); } }

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