9- separate files, independent compilation, header files

Question 1

Executable statements

Answer 1

some corresponding machine code is generated by the compiler
example: assignment statements, looping/branching constructs, function invocations

Question 2

Non-executable statement

Answer 2

no machine code generated
example: function prototypes, variable and constant declarations, #include directives

Question 3

include directives

Answer 3

tell the compiler to include specified file. The files included are called include or header files and have extensions .hpp
two forms:
#include <filename> - file is found in standard system-dependent location
#include ”filename.hpp” - file is found in the same directory as the rest of the code
purpose of include files: centralize declarations</filename>

include files may also contain include directives
what to put in include files: non-executable statements
what not to put in include files: executable statements, function definitions

Question 4

Symbol table

Answer 4

which function code the file contains

Question 5

External references

Answer 5

which functions the file uses but whose code is missing

Question 6

entry point

Answer 6

function where the execution starts – main()

Question 7

linker

Answer 7

locates the object file with the entry point
adds to executable
examines external references of this object file
for each external reference, searches other files/libraries’ symbol tables to find required function
when located, adds to executable
continues this process for other files

Question 8

Preprocessor directive

Answer 8

starts with hastag symbol #, cause compiler to do manipulation of source file before compilation
#include is a preprocessor directive ‘
not a C++ statement

Question 8

define [name value]

Answer 8

value textual substitution of name by value
seldom used for primary purpose
do not use #define instead of global constants
problem: #define press 50+5
int myvar = press * 20; // changes order of operations
value may be skipped: #define BIG_NAME

Question 9

ifdef [name]

Answer 9

true if name defined

Question 10

ifndef [name]

Answer 10

• true if not
  this text is included in compiler processing if true, skipped otherwise

Question 11

endif

Answer 11

completes #if

Question 12

Include guards

Answer 12

preprocessor directives used for multiple inclusion protection