Size Counters

Although it is relatively easy to count the sizes of small programs, manually count-ing even small programs can be time-consumcount-ing and error-prone. For large pro-grams, however, manual counting is impractical, making automated size counters essential.

Counters can be designed to count the number of almost any product element as long as the definition for that element is precise and specific. For example, a

TABLE 3.3 VARIATIONS IN LOC PRODUCTIVITY

Size Productivity

Productivity Option LOC LOC/Hour

Added (350+100+50) 500 8.33

Added + Modified (500+100) 600 10.00

Added + Modified + Deleted (600+200) 800 13.33

Added + Modified + Reused (600+600) 1200 20.00

Added + Modified + Deleted + Reused (1,200+200) 1400 23.33

Total Finished Product 900 15.00

LOC counter could count physical lines or logical lines. Although automatically counting database elements can be a bit more complex, if the object model is accessible, you can usually count selected sets of database elements.

Physical LOC Counters

The simplest type of size counter counts physical LOC. Here, you count all text lines except comments and blank lines. A text line that has both comments and source code is counted as one LOC.

Logical LOC Counters

Logical LOC counters work much like physical counters except that line-counter stepping is more complex. My Object Pascal logical line counter had 939 LOC and took me about 50 hours to develop. Don’t try to develop a logical line counter unless you have plenty of time to do it. Although people can endlessly debate the best way to count LOC, the details are not that important. The key is to be precise and consistent. In my Object Pascal and C++ programs, I counted every logical program statement. Although some may argue that counting begin and end state-ments is not a good idea, this is a matter of personal preference. If you could show, however, that the time required to develop a program had a higher correlation with LOC when begin-end pairs were counted than when they were not, that would be a good reason to use them. This would also be the proper way to resolve almost any size counting question.

Presently, there is no compelling evidence to support any one counting method over any other. With good data, however, a study of the various alterna-tives could quickly show which, if any, would be best for your work. It may show, as is likely, that many different approaches produce roughly equivalent results.

In that case, the selection is arbitrary. The fact that it is arbitrary, however, does not mean that everyone should do it differently. If all of the projects in an organi-zation used the same counting standard, they could afford to develop a single high-quality automated counter for everyone to use. They would also have a much larger volume of data to use in planning and quality analysis.

Counting Program Elements

It is often desirable to measure the sizes of various parts of large programs. For example, if you intended to reuse some newly developed classes or procedures, you would like to know how large each one is. As you will see in Chapter 5, such counts can also help with size estimating.

3.7 Size Counters 49

To maintain separate counts for each class or procedure, you must determine where each one starts and ends. Because the way to do this depends on the pro-gramming language, there is no general guideline. The counter I built for Object Pascal recognized the keywords procedure, function, constructor, and destruc-tor as the beginning of procedures. I found the endpoints by counting begin-end pairs. With a little study, you can determine the indicators for the beginning and ending points of the methods, procedures, classes, functions, or other elements for the language you use. You can then use this definition to scan the program text and start and stop the size counter at the appropriate points.

Using Coding Standards and Physical LOC Counters

One simple way to count logical LOC is to use a coding standard and count phys-ical LOC, omitting comments and blanks. The idea is to write the source code with a separate physical text line for every countable line. Then, when you count phys-ical lines, you are also counting logphys-ical lines. To use this method, you must care-fully follow a coding standard like the example shown in Table 3.4. If, at the same

TABLE 3.4 EXAMPLE C++ CODING STANDARD

Purpose: To guide the development of C++ programs Program Headers Begin all programs with a descriptive header.

Header Format /*************************************************************************/

/* Program Assignment: the program number */

/* Name: your name */

/* Date: the date program development started */

/* Description: a short description of the program */

/* function */

/*************************************************************************/

Listing Contents Provide a summary of the listing contents.

Contents Example /*************************************************************************/

/* Listing Contents: */

/* Reuse instructions */

/* Modification instructions */

/* Compilation instructions */

/* Includes */

/* Class declarations: */

/* CData */

/* ASet */

/* Source code in c:\classes\CData.cpp: */

/* CData */

/* CData() */

/* Empty() */

/*************************************************************************/

3.7 Size Counters 51

Reuse Instructions • Describe how the program is used. Provide the declaration format, parameter values and types, and parameter limits.

• Provide warnings of illegal values, overflow conditions, or other conditions that could potentially result in improper operation.

Reuse Example /*************************************************************************/

/* Reuse Instructions */

/* int PrintLine(char *line_of_character) */

/* Purpose: to print string, ‘line_of_character’, on one print line */

/* Limitations: the maximum line length is LINE_LENGTH */

/* Return: 0 if printer not ready to print, else 1 */

/*************************************************************************/

Identifiers Use descriptive names for all variables, function names, constants, and other identifiers. Avoid abbreviations or single letter variables.

Identifier Example int number_of_students; /* This is GOOD */

float x4, j, ftave; /* These are BAD */

Comments • Document the code so that the reader can understand its operation.

• Comments should explain both the purpose and behavior of the code.

• Comment variable declarations to indicate their purpose.

Good Comment If (record_count > limit) /* have all the records been processed? */

Bad Comment if(record_count > limit) /* check if record_count is greater than limit */

Major Sections Precede major program sections by a block comment that describes the processing that is done in the next section.

Example /*************************************************************************/

/* This program section will examine the contents of the array */

/* “grades” and will calculate the average grade for the class. */

/*************************************************************************/

Blank Spaces • Write programs with sufficient spacing so that they do not appear crowded.

• Separate every program construct with at least one space.

Indenting • Indent every level of brace from the previous one.

• Open and close braces should be on lines by themselves and aligned with each other.

Indenting Example while (miss_distance > threshold) {

time, you also follow consistent formatting standards, you will get highly read-able code. Note, however, that when you count LOC this way, you cannot refor-mat the code without changing the LOC count.

One problem with this approach is caused by instructions that span multiple text lines. Because the LOC counter will count each line, you will get too large a count. In these cases, either modify the counter to recognize multi-line instruc-tions, write a true logical LOC counting program, or count these cases by hand. If multi-line instructions are rare in your programs, the easiest approach is to ignore the problem and trust your estimating method to allow for those cases. If such in-structions are common, however, you should either count the cases by hand or ad-just your counter to properly count multi-line instructions.

Counting Deletions and Modifications

One of the more difficult counting problems is keeping track of the additions, dele-tions, and changes in multiversion programs. For small programs, you can manu-ally count the added and modified elements, but for large programs this is impractical. Even for small programs, such manual counts are almost impossible unless you do the counting immediately after completing each modification.

One approach is to flag each program line separately with a special comment.

A special counter could then recognize these flags and count the added and deleted product elements. Although nice in theory, this approach is impractical. While modifying a program, you will find it almost impossible to remember to comment every addition and deletion. It is even more difficult to remember to do it when you are fixing defects in testing. A second alternative is both practical and con-venient, but it involves a bit of programming. Here, you use a special program counter to compare each new program version with its immediate predecessor and insert appropriate flags.

Because this comparator could not easily recognize whether a new line was a modification or an addition, all modifications would be counted as deletions and

TABLE 3.4 (continued )

Capitalization • Capitalized all defines.

• Lowercase all other identifiers and reserved words.

• Messages being output to the user can be mixed-case so as to make a clean user presentation.

Capitalization #define DEFAULT-NUMBER-OF-STUDENTS 15 Example

int class-size = DEFAULT-NUMBER-OF-STUDENTS;

additions. This is exactly equivalent to the LOC accounting rules. You could even run the comparator counter after every modification and defect fix.

Another approach is to build such a comparator counter into the source-code control system. That way, every program update would be analyzed and every line automatically flagged with the date and version when it was added or deleted. You could also assign a number to every program fix, release, or version update and affix that number and date to every deleted, added, or modified line in each update.

You could also include the developer’s name, the fix number, the project name, or any other potentially useful information. With such a support system, you could determine when every change was made, when a defect was injected, or how much code was added and deleted with each update. These data are essential for effec-tive quality management of large programs. Modern source-code control systems generally provide many of these capabilities.

Overall, the problem of counting deletions and modifications can be partially addressed with tool support, but it is still a difficult process that is both error-prone and apt to produce misleading results. The best approach is to make an accurate count for each small program and then use whatever automated tools you can ob-tain to identify and track all subsequent changes.