Download Programming Development Environment

ECE 101
Exploring Electrical Engineering
Chapter 9
Programming Development Environment
Herbert G. Mayer, PSU
Status 3/1/2016
Syllabus
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What is a Program?
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What is a Computer?
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Holding Data
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Programming Languages
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Machine Language Sample
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Compiler
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Linker
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Loader
What is a Program
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A computer program is a sequence of executable
machine instructions, reading information (input),
computing new data, and generating output,
according to the steps of an algorithm
An algorithm is a finite sequence of instructions,
reading information (input), computing new data, and
generating output
The two are almost synonymous, except that the
program executes (AKA runs) on a computer, the
algorithm is just an abstraction in our mind or written
on paper
What is a Program
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The algorithm coded in a programming language
becomes your program (noun)
Why relevant to Electrical Engineers?
Sooner or later you will acquire programming skills
Either in a general purpose programming language
Or a special programming language controlling a
connected board
Can be external or inserted internal into backplane of
a computer
But you will program (verb) eventually
What is a Computer
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A computer is a physical device that can read input, compute,
and produce corresponding output
It “understands” a small set of machine instructions, which it
can execute, one at a time (for a uni-processor)
It is possible, but very tedious, to write a program in such
machine instructions
An Assembler eases this tediousness by allowing users to write
abstract data and symbolic instructions, which the assembler
then translates into machine code
A compiler (similar: an interpreter) reads higher-level programs
and maps them into assembly code; or sometimes into machine
code directly
And you, EEs, will design and build the next generation of
computers
What is a Computer
Main Memory
(RAM, ROM)
Input
Processor
Output
(e.g., keyboard, mouse)
(CPU)
(e.g., monitor, printer)
Auxiliary Storage
(e.g., disk drives)
Computer’s Processor – CPU or ALU
Instruction
Decoder
Memory
Interface
Registers
(fast storage)
ALU
The ALU (Arithmetic Logic Unit) performs basic
arithmetic, logic, and comparison operations.
To main
memory
Holding Data
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A computer holds a good amount of data in memory
The size of such a memory (AKA primary storage) is
defined by the architecture’s address range
E.g. on a 32-bit architecture, memory can be as large
as 232 different addressable units
Often such units are bytes, i.e. 8-bit addressable,
contiguous units; other architectures use 60-bit words
Large amounts of data are stored on secondary
storage devices, such as rotating disks or SSDs
Access to data in memory is slow, about 10-100 times
slower than executing one instruction
Access to data on disk is even 10,000s of times slower
Holding Data
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Getting data from memory into the processor
(usually a machine register) is called a load
operation
Moving data from a register to memory is called a
store operation
Such transport proceeds on a bus; the width of the
bus and its speed are critical for the overall
execution speed of the machine and thus of your
programs
Programming Languages
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Even writing assembly source code is highly tedious
Since the 1960s, higher-level programming
languages have been developed
Some of these are machine-independent; others
highly machine-dependent (AKA architecturedependent), e.g. C++ or Java
A machine-independent language allows writing of
source programs (code) that can be executed on
different machines, provided a compiler is available
on each
This is referred to a portability of source programs,
quite a desirable property!
Programming Language Milestones
C Language Milestones
1969 to 1973 – C (Bell Labs initial development)
1978 – K&R C (Kernighan and Ritchie)
1989 – C89 (ANSI)
1990 – C90 (ISO)
1995 – C90 Normative Amendment 1 → "C95”
1999 – C99 (ISO)
2011 – C11 (ISO)
Machine Language Sample
600:
602:
603:
605:
A9 5A
18
69 20
8D 00 10
LDA #$5A
CLC
ADC #$20
STA $1000
;
;
;
;
Load accumulator with number
Clear carry flag
Add $20 to accumulator w/carry
Store accumulator at $1000
Assembler translates an assembly program to machine
language
Assembly language still requires a high level of
programmer expertise
Compiler
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Compiler is a special-purpose system program that
reads source programs, written in the source
language and translates them into machine language
Mapping into machine language (AKA object code)
sometimes involves an intermediate step: Creating
assembly source first, and then using the assembler
to generate machine code
A compiler generally understands just one input
language; exceptions are some C++ compilers that
also read C source
Compilers emit error messages when certain
violations are detected, referring messages to line
numbers
Compiler
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Source files contain the C++ program code
 .cpp extension (file is in text format); also .c
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Header files can contain prototypes, macros, data
type declarations, or source code
 .h extension (file is in text format)
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Object files contain intermediate compiled code
 .o -or- .obj extension
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Executable files contain runnable binary code
 .out -or- .exe -or- no extension
Compiler
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preprocessor → handles preprocessor directives and
expands macro definitions
compiler → takes preprocessed source code files and
translates them to intermediate code; for beginners it is
convenient to view the other system programs as part of
the compiler
assembler → takes intermediate code files and
translates them to binary object code
linker → resolves references among the object files and
the libraries. It puts all the parts together to create the
single, final, executable object file
Compiler
prog_1.o
prog_1.c
prog_2.o
prog_2.c
Preprocessor
Compiler
Assembler
Linker
prog_3.c
etc.
User
Header files
prog_1.h
prog_2.h
prog_3.h
etc.
Executable
file
Object files
Source files
prog
prog_3.o
etc.
Library
Header files
Library files
stdio
stdio.h
stdlib.h
math.h
etc.
stdlib
math
etc.
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Linker
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Often programs are composed of multiple source
programs
For example, some projects are too large to have a
single programmer develop all code in sequence
Also system function, such as input, output, heap
acquisitions etc. are provided in the PDE, and do
need to be coded by the programmer
All such elements are linked together into a single,
executable object program
That is the work of the system’s linker
For C or C++ on Unix the link step is frequently
hidden, i.e. not visible to the programmer
Loader
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When a program has been linked, it is still
not executing, not even loaded!
Instead, it is just a binary file, residing on
some disk, as an object file, but ready to run
To run such object code, it must be loaded
into memory and be granted processor
execution time
That is the purpose of the system loader
Generally, the loader and load function are
not directly visible to the user = programmer
Example: Vintage CPU (1975)
Pin-out
Die Shot
MOS 6502
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Chuck Peddle at MOS
Single core
8-bit data
Memory
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64 KB main
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Registers:
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Accumulator (A)
Index (X, Y)
Processor Status (P)
Stack Pointer (S)
Program Counter (PC)
Speed: 1 to 2 MHz <- not a typo!
Process: 8 m
# of transistors: ~3500
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Example: Modern CPU (2013)
Intel i7-4770 Haswell
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Package
Four cores = processors = CPUs
64-bit data
Memory
4x256 KB L2 cache
 8 MB L3 cache
 32 GB main (3.2x107 KB)
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Registers:
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Die Shot
8 32-bit
16 64-bit
Integrated GPU
Speed: 3.4 GHz (3400 MHz)
Process: 22 nm (0.022 m)
# of transistors: ~1.4 billion
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