1. Introduction CS 104: Applied C++ What is Programming? For some given problem: __________ a solution for it -- identify, organize & store the problem's __________ -- develop _______________ (procedures) to process it; ______ this solution as a program; ______ the program; __________ the program (fix it, upgrade it, …). What is a program? — a collection of statements that — implement the design plan, and — are written in a programming language — a language that the computer can understand. (Read Chap. 1 1 1

2. What kinds of statements do computers understand? 2 A computer only understands a language specially designed for it called _______________ language. Machine-language statements are stored in a computer’s memory, which is a sequence of two-state devices (on-off switches). They are retrieved from memory and executed one at a time. The "character set" for machine language: ___ representing "off" ___ representing "on" RISC CISC 2

3. Machine language programs thus consists of strings of _________ (____________________) 3 Example (hypothetical) 000100000000000000000100000000101001001 000000000000001000000000100100011000000 000000010000000010000100010000000000000 100000000110001000000000011010001000000 000000100100000000000000010000011001001 000110000000000000100000000100001000100 000000100001000000001100011100000000000 0010... 3

4. Bits are usually grouped into _________ (8 bits) and __________ (e.g., 32 or 64 bits). Each machine language instruction might be stored in one word. 4 opcod e 000100000000000000010100000000000001001 000000000000001000000000100100011000000 000000010000000010000100010000000000000 100000000110001000000000011010001000000 000000100100000000000000010000011001001 000110000000000000100000000100001000100 000000100001000000001100011100000000000 0010... instruction #1 first operandsecond operand e.g., "Store" 1 in memory location with this address 4

5. So a sequence of machine language instructions might be stored in a sequence of consecutive words. 5 000100000000000000010100000000000001001 000000000000001000000000100100011000000 000000010000000010000100010000000000000 100000000110001000000000011010001000000 000000100100000000000000010000011001001 000110000000000000100000000100001000100 000000100001000000001100011100000000000 0010... instruction #1 #4 #3 #2 5

6. A Real Machine-Language Example 6 SPARC executable machine code 000001110111010100000101 000001000110000100000110 000000000000010000000010 000000000000010000000000 000000000000000000000000 000000000000000000000010 000000000000000000000000 000000000000000000000001 000000000000000000000001 000000000011010000110000 000000000000000000000000 000000000000000001100100 000000000000000000000000 000000010011000100100100 000000000000000000000000 000000000000000001100100 000000000000000001000000 000000000000000000000101 000000000000000001010000 000000000000000000110011 000000000000000000110001 000000000000000000000000 000000000000000000000110 000000000000000000000000 000000000000000001100100 000000000000000000000001 000000000000000001100100 000000000000000000000000 000000000000000000000000 000000000000001001000000 000000000000000000000000 000000000000000000000101 000000000000000000000000 000000000000000000000000 000000000000000000000011 000000000000000000000000 000000000000001100100100 000000000000000000000000 000000000000000000000000 000000000000000000100001 … this goes on for another 1600 lines... Intel Pentium executable machine code 000000100111000000010001 000001100100010101000110 000001100010010101010100 000000100001000000010001 000001100111000101010001 000001110001000101100100 000000100111000101010111 000000100001000101000011 000000000101000000010101 000001100001010101000111 000000110001000101000011 000001100001010100110111 000001100110010101010111 000001100100010101100000 000001100010010101010100 000000100111000101000100 000000000110010001110010 000001010111010000010010 000001010111010100110111 000001100111000101000111 000001010111010101100101 000001100111010101000011 000001110000000101010101 000001100110000101010001 000001100010000101000101 000001100001010100110111 000000000110010001110010 000000000100010000010010 000001100010000001010110 000001100011000101000101 000001010111010000010001 000001010111010100110111 000001100000010101010101 000001100111000101010001 000000000100010001110011 000001110001010001010110 000001100110000101000011 000000110001000000010001 000000000100010001110011 000001110010000001010110 000001110000000101110001 000000000100010101000101 000000110001000001100011 000000000100010001110011 000001100010010001010110 000001100010000101010110 000001100011000101000101 000000000101000000010101 000001110010000001010110 000001110100000101000101 000000000110010101100100 000000000100010000010010 … this goes on for another 74 lines... int main() { int x, y; x = 1; y = x + 2; return 0; } C++ 6

7. Early Computers Required a programmer to write in machine language –Very easy to make mistakes! –And they were hard to find! –Programs were not ___________ They could only be run on one kind of machine! Result: programming was very difficult and programs weren't widely used. 7 7

8. An Early Innovation Devise a set of mnemonics (abbreviations), one for each machine language instruction; this was called an _____________ language Create a machine-language program called an ___________to input each assembly language instruction and translate it into machine language. 1000000010101001 1100010000000010 1000000110111100 LOAD x ADD 2 STORE y Assembler 8 8

9. 9 The Real Example Intel Pentium assembly language: _main: pushl %ebp movl %esp,%ebp subl $24,%esp call ___main movl $1,-4(%ebp) movl -4(%ebp),%eax addl $2,%eax movl %eax,-8(%ebp) xorl %eax,%eax jmp L2.align 4 L2: movl %ebp,%esp popl %ebp ret 000001110111010100000101 000001000110000100000110 000000000000010000000010 000000000000010000000000 000000000000000000000000 000000000000000000000010 000000000000000000000000 000000000000000000000001 000000000000000000000001 000000000011010000110000 000000000000000000000000 000000000000000001100100 000000000000000000000000 000000010011000100100100 000000000000000000000000 000000000000000001100100 000000000000000001000000 000000000000000000000101 000000000000000001010000 000000000000000000110011 000000000000000000110001 000000000000000000000000 000000000000000000000110 000000000000000000000000 000000000000000001100100 000000000000000000000001 000000000000000001100100 000000000000000000000000 000000000000000000000000 000000000000001001000000 000000000000000000000000 000000000000000000000101 000000000000000000000000 000000000000000000000000 000000000000000000000011 000000000000000000000000 000000000000001100100100 000000000000000000000000 000000000000000000000000 000000000000000000100001 Intel Assembler SPARC assembly language: main: save%sp, -120, %sp mov1, %o0 st%o0, [%fp-20] ld[%fp-20], %o0 add%o0, 2, %o1 st%o1, [%fp-24] mov0, %i0 b.LL2 nop mov0, %i0 b.LL2 nop.LL2: ret restore 000000100111000000010001 000001100100010101000110 000001100010010101010100 000000100001000000010001 000001100111000101010001 000001110001000101100100 000000100111000101010111 000000100001000101000011 000000000101000000010101 000001100001010101000111 000000110001000101000011 000001100001010100110111 000001100110010101010111 000001100100010101100000 000001100010010101010100 000000100111000101000100 000000000110010001110010 000001010111010000010010 000001010111010100110111 000001100111000101000111 000001010111010101100101 000001100111010101000011 000001110000000101010101 000001100110000101010001 000001100010000101000101 000001100001010100110111 000000000110010001110010 000000000100010000010010 000001100010000001010110 000001100011000101000101 000001010111010000010001 000001010111010100110111 000001100000010101010101 000001100111000101010001 000000000100010001110011 000001110001010001010110 000001100110000101000011 000000110001000000010001 000000000100010001110011 000001110010000001010110 000001110000000101110001 000000000100010101000101 000000110001000001100011 000000000100010001110011 000001100010010001010110 000001100010000101010110 000001100011000101000101 000000000101000000010101 000001110010000001010110 000001110100000101000101 000000000110010101100100 000000000100010000010010 Sun Assembler 9

10. Assembly Languages Allowed a programmer to use mnemonics, which were more natural than binary. +Much easier to read programs +Much easier to find and fix mistakes –Still ______________ to different machines –Still quite difficult to write, read, and debug programs 10

11. To improve on assembly language: Devise a set of statements called a ____________ language that are closer to __language and methods of writing expressions and A program called a ___________to translate them into machine language. 11 Why not just use human language? It’s too complex and ambiguous; e.g., “Time flies like an arrow” Next Major Advance: High Level Languages & Compilers 11

12. Compilers vs. Assemblers An assembler translates one assembly-language statement into ______ machine-language statement. A compiler translates one high-level statement into ______________ machine-language statements so it is much more difficult to write a correct compiler than an assembler. LOAD b ADD c STORE temp1 LOAD a MULT temp1 STORE z Assembler 1000000000110101 1100010000110110 1000000101000001 1000000000110100 1100011001000001 1000000100110111 z = a * (b + c); Compiler 12

13. With programming in high-level languages (e.g., C++): +Programs are much easier to read. +Mistakes are much easier to find and fix. +Programs are (or can be) ___________from one machine to another (provided they conform to the language standard). Just need a compiler for that language written in the machine language of that machine.  Not so simple that just anyone can use them (otherwise this course wouldn't exist) 13 Advantages of High-Level Languages 13

14. Objectives in Programming A program to solve a problem should be: +correct (it actually solves the problem) +readable (understandable by another person) +user-friendly (designed in a way that is easy for its user to use). 14 Grading criteria Later +efficient (doesn’t waste time or space) 14