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CS-135 Part 2
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- 1Why does less thought through architecture help XPfunctionality can change during development
Architecture revision might turn out cumbersome - 2What are the advantages to pair programmingkeep each other on task
brainstorm refinements to the system
clarify ideas
take initiative when their partner is stuck thus lowering frustration
hold each other accountable to the teams practise - 3What is Swinga GUI widget toolkit for Java.
- 4Why does software have different versions?different releases of the product,
variations for different platforms (H+S)
versions within development cycle
(test release, alpha, beta)
Each edit of the program - 5What does version control do?tracks changes to a set of files
- 6what 7 things does version control store?work on a local checkout
recover code at a certain time
branch development
merge existing branches
to see who made changes
all versions can exist simultaneously in central repository
store changes with minimal space - 7Why use version controlUSEFUL:
-want old versions
-track project history
-teams can work on the same code - 8what is branchingwhen there are two lines of development
- 9what is merging or updatingwhen two branches come back together
- 10what is a check out ?a local working copy of a project, outside of the version control system.
- 11Why do programmers use check outs?the local versions isolate developers from each other's possible unstable changes
- 12what happens when programmers check in?all changes are merged back, - copied back into the version control system. Sometimes test suites are run automatically on the result of the check in, if the test fails the changes are not accepted.
- 13If you build your code on a library and then the library is updated what happens?the library branches. you then have to merge the two branches back together
- 14What is a project/ repository?a set of files in version control
- 15does version control require a specific type of file?No, just manages versions of a collection of files. Generally works better on text files as opposed to binary files
- 16what is the method to changing a filecheck out file
edit it
check the file back into the central repository.
Creates a new version of the file and increments the version number - 17How big should edits be?SMALL. only change one thing at a time. then we can write change/commit messages that describe the change
- 18do version control systems store the whole file each time a change is made?no, they store the changes,
- 19why do version control systems only store the changes made to a filefor efficiency.
stores differences from previous version
minimises space
makes check-in, check-out potentially slower.
Must apply differences from all previous versions to compute current file - 20for each revision made, what 6 things are stored1) differences for that version
2) new version number
3) (metadata) Author
-time of check in
-log file message
-results of smoke test. (validating code changes) - 21define smoke testingtesting new code to see if the changes made will work and do not cause errors. its a cost effective way to ensure identifying and fixing bugs.
- 22Is a new branch formed every time code is checked inNo, changes are merged into main code line.
- 23can branches be formed by accident?no! must explicitly ask to create branch
- 24what are the two possible outcomes of an updatesuccess
failure due to conflicts - 25if two people are merging data one after the other, when will there be a conflictif changing the order in which the changes apply are not equal.
- 26What happens when there are conflctsthe system cannot apply changes
- 27what are two types of conflictsthe final result is not unique
depends on order in which changes are applied - 28how can conflicts be resolvedby hand
- 29when do conflicts happen, what are they based onnearness of changes -
changes made to the same line - 30do conflicts take note of changes to whitespaceno
- 31if there are no conflicts does that mean the changes work togetherno
e.g. if A changes paraments (int a, int b) to (int a, int b, int c)
and B calls (a, b). Version control will not pick this up - 32is merging syntacticyes
- 33will semantic errors be picked up in version controlpossibly not
- 34name 2 version control systemsSubversion (svn) - centralised CS
Git - distributed CS - 35What are the main features of SVNcentral server stores the main repository
users checkout local working copies
user makes changes to local working copy
users check in changes to main repository.
During commit either all selected files are checked in or none are. repository has a version number which ++ each commit - 36Name 2 subVerison featuesbranches
tags - can label a repository version with a unique name (are actually branches you do not do any further development on) - 37svn issuesif the server goes down, no-one can commit changes. If each work on their local copys there is a lot more to commit later on. then rolling back is a problem, all or nothing
- 38how does GIT workno central repository
people commit locally then push their commits to other repository.
you can push to others repository
you can pull changes from others - 39GIT Feauturesbranches
tags-just labels
conflicts easier to handle, as changes committed locally first
FLEXIBILITY - many ways to work with
-difficult to learn
cherry picking
rebasing etc. - 40What is software matricsengineering approach to software engineering, providing quantitative and objective base that software engineering was lacking
- 41how does software matrics use measurementsby assessment and prediction.
1. monitoring the advancement of a project in order to take the appropriate corrective decisions
2. evaluating a software product or process - 42How does software metrics help a manager?provide manager with quantitative support to decisions that were previously taken on the basis only of subjective factors
- 43name some of the 28 traditional metrics listed in Xenos SURVEYAML -average module length
COC -conditions and Operations count
ERE -extent of reuse
NLE -Nesting levels - 44What internal attributes do we want to measure in SE?internal attributes of code
CODE SIZE, CONTROL FLOW COMPLEXITY, reuse modularity, coupling, cohesion - 45what external attributes do we want to measureReliability, usability, resusability, maintainability
- 46Name the four metrics we are interested inLOC (Lines of code)
Density of comments
Average LOC per method
Cyclomatic Number - 47What are the positivies to LOC metricsimple
ease of application
LOC correlates with effort
suggested that it is a good indicator - 48Why does LOC help good formattingLonger lines of code get penalized
- 49What is a line of codeincludes any line of code that is not comment or blank line, regardless of number of statements on that line. Included program headers, declarations, and executable and non-executable code.
- 50Problems with LOCignores goodness of code,
short and well-designed programs are punished.
Hard to directly compare programs in different langauges. - 51what formula is density of comments metric based onCLOC/NLOC
CLOC -number of comment lines
NLOC - number on non-comment lines - 52What is the metric average line of code per methodnumber of lines in method/number of methods
- 53what makes a good metric?Property 4: functionality is not the same as complexity
5: monotonicity with respect to program concatenation - 54What is the Cyclomatic numbernumber of edges - number of nodes + 2
Represents the number of linearly independent paths through G - 55why is the cyclomatic number usefuluseful to determine how hard a method will be to maintain / test
-doubtful as an objective measure of complexity. - 56whats McCabe's suggestion of cyclomatic number in a moduleno more than 10
- 57if the cyclomatic number is higher, what does this suggestmore updates required
- 58who used cyclomaticchannel tunnel rail system - if cyclomatic number was more than 20 , or more than 50 statements, the module was rejected
- 59what are linearly independent paths?1. add an edge from the sink node to the source node. There is a path between any pair of nodes.
2.as the graph has a finite number of edges (n), we can encode them - 60How do we encode paths by n-tuplesgiven a directed path p, we cna represent it as an n-tuple (x1, x2, xn) where Xi says how often edge i appears in p.
- 61What does linear combination of paths mean?Xn = A1Y1,n + ....+AkYk,n
- 62what is linear independencea set of paths is linear independent if no path in the set is a linear combination of any other paths in the set..
- 63what is a basis set of cyclesa maximal linearly independent set of cycles
- 64define strongly connecteda graph is strongly connected if for all nodes n1 does not equal n2, it holds that there exists a path from n1 to n2
- 65What is the formaula in a strongly connected graph (V, E)THE BASIS SET HAS |E| -|V| + 1 cycles
- 66—
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- Fichas sobre CS-135 Part 2, creado por liz simpson el 01/06/2018.
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- liz simpson
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