Capability Maturity Model Integration

1. What is CMMI and what's the advantage of implementing it in an organization?
   CMMI stands for Capability Maturity Model Integration. It is a process improvement approach that provides companies with the essential elements of an effective process. CMMI can serve as a good guide for process improvement across a project, organization, or division.

   CMMI was formed by using multiple previous CMM processes. 

   
   

   The following are the areas which CMMI addresses:

   
   

   

   
   

   Systems engineering: This covers development of total systems. System engineers concentrate on converting customer needs to product solutions and supports them throughout the product lifecycle.

   
   

   Software engineering: Software engineers concentrate on the application of systematic, disciplined, and quantifiable approaches to the development, operation, and maintenance of software.

   
   

   Integrated Product and Process Development (IPPD): Integrated Product and Process Development (IPPD) is a systematic approach that achieves a timely collaboration of relevant stakeholders throughout the life of the product to better satisfy customer needs, expectations, and requirements. This section mostly concentrates on the integration part of the project for different processes. For instance, it's possible that your project is using services of some other third party component. In such situations the integration is a big task itself, and if approached in a systematic manner, can be handled with ease.

   
   

   Software acquisition: Many times an organization has to acquire products from other organizations. Acquisition is itself a big step for any organization and if not handled in a proper manner means a disaster is sure to happen.
2. What's the difference between implementation and institutionalization?
   Both of these concepts are important while implementing a process in any organization. Any new process implemented has to go through these two phases.

   

   Implementation: It is just performing a task within a process area. A task is performed according to a process but actions performed to complete the process are not ingrained in the organization. That means the process involved is done according to the individual point of view. When an organization starts to implement any process it first starts at this phase, i.e., implementation, and then when this process looks good it is raised to the organization level so that it can be implemented across organizations. 

   
   

   Institutionalization: Institutionalization is the output of implementing the process again and again. The difference between implementation and institutionalization is in implementation if the person who implemented the process leaves the company the process is not followed, but if the process is institutionalized then even if the person leaves the organization, the process is still followed.
3. Can you explain the different maturity levels in a staged representation?
   There are five maturity levels in a staged representation as shown in the following figure.

   
   

   Maturity Level 1 (Initial): In this level everything is adhoc. Development is completely chaotic with budget and schedules often exceeded. In this scenario we can never predict quality. 

   
   

   Maturity Level 2 (Managed): In the managed level basic project management is in place. But the basic project management and practices are followed only in the project level.

   
   

   Maturity Level 3 (Defined): To reach this level the organization should have already achieved level 2. In the previous level the good practices and process were only done at the project level. But in this level all these good practices and processes are brought to the organization level. There are set and standard practices defined at the organization level which every project should follow. Maturity Level 3 moves ahead with defining a strong, meaningful, organizational approach to developing products. An important distinction between Maturity Levels 2 and 3 is that at Level 3, processes are described in more detail and more rigorously than at Level 2 and are at an organization level.

   
   

   Maturity Level 4 (Quantitatively measured): To start with, this level of organization should have already achieved Level 2 and Level 3. In this level, more statistics come into the picture. Organization controls the project by statistical and other quantitative techniques. Product quality, process performance, and service quality are understood in statistical terms and are managed throughout the life of the processes. Maturity Level 4 concentrates on using metrics to make decisions and to truly measure whether progress is happening and the product is becoming better. The main difference between Levels 3 and 4 are that at Level 3, processes are qualitatively predictable. At Level 4, processes are quantitatively predictable. Level 4 addresses causes of process variation and takes corrective action.

   
   

   Maturity Level 5 (Optimized): The organization has achieved goals of maturity levels 2, 3, and 4. In this level, processes are continually improved based on an understanding of common causes of variation within the processes. This is like the final level; everyone on the team is a productive member, defects are minimized, and products are delivered on time and within the budget boundary.

   
   

   The following figure shows, in detail, all the maturity levels in a pictorial fashion.

   

Software Testing Basics

1. Can you explain the PDCA cycle and where testing fits in?
   Software testing is an important part of the software development process. In normal software development there are four important steps, also referred to, in short, as the PDCA (Plan, Do, Check, Act) cycle.

   

   Let's review the four steps in detail.

   1. Plan: Define the goal and the plan for achieving that goal.
   2. Do/Execute: Depending on the plan strategy decided during the plan stage we do execution accordingly in this phase.
   3. Check: Check/Test to ensure that we are moving according to plan and are getting the desired results.
   4. Act: During the check cycle, if any issues are there, then we take appropriate action accordingly and revise our plan again.

   
   

   So developers and other stakeholders of the project do the "planning and building," while testers do the check part of the cycle. Therefore, software testing is done in check part of the PDCA cyle.
2. What is the difference between white box, black box, and gray box testing?
   Black box testing is a testing strategy based solely on requirements and specifications. Black box testing requires no knowledge of internal paths, structures, or implementation of the software being tested.

   
   

   White box testing is a testing strategy based on internal paths, code structures, and implementation of the software being tested. White box testing generally requires detailed programming skills.

   
   

   There is one more type of testing called gray box testing. In this we look into the "box" being tested just long enough to understand how it has been implemented. Then we close up the box and use our knowledge to choose more effective black box tests.

   
   

   

   
   

   The above figure shows how both types of testers view an accounting application during testing. Black box testers view the basic accounting application. While during white box testing the tester knows the internal structure of the application. In most scenarios white box testing is done by developers as they know the internals of the application. In black box testing we check the overall functionality of the application while in white box testing we do code reviews, view the architecture, remove bad code practices, and do component level testing.
3. Can you explain usability testing?
   Usability testing is a testing methodology where the end customer is asked to use the software to see if the product is easy to use, to see the customer's perception and task time. The best way to finalize the customer point of view for usability is by using prototype or mock-up software during the initial stages. By giving the customer the prototype before the development start-up we confirm that we are not missing anything from the user point of view.

   
   

   
4. What are the categories of defects?
   There are three main categories of defects:

   

   1. Wrong: The requirements have been implemented incorrectly. This defect is a variance from the given specification.
   2. Missing: There was a requirement given by the customer and it was not done. This is a variance from the specifications, an indication that a specification was not implemented, or a requirement of the customer was not noted properly.
   3. Extra: A requirement incorporated into the product that was not given by the end customer. This is always a variance from the specification, but may be an attribute desired by the user of the product. However, it is considered a defect because it's a variance from the existing requirements.

Operating Systems

1. Explain the concept of Reentrancy?
   It is a useful, memory-saving technique for multiprogrammed timesharing systems. A Reentrant Procedure is one in which multiple users can share a single copy of a program during the same period. Reentrancy has 2 key aspects: The program code cannot modify itself, and the local data for each user process must be stored separately. Thus, the permanent part is the code, and the temporary part is the pointer back to the calling program and local variables used by that program. Each execution instance is called activation. It executes the code in the permanent part, but has its own copy of local variables/parameters. The temporary part associated with each activation is the activation record. Generally, the activation record is kept on the stack.

   Note: A reentrant procedure can be interrupted and called by an interrupting program, and still execute correctly on returning to the procedure.
2. Explain Belady's Anomaly?
   Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.
3. What is a binary semaphore? What is its use?
   A binary semaphore is one, which takes only 0 and 1 as values. They are used to implement mutual exclusion and synchronize concurrent processes.
4. What is thrashing?
   It is a phenomenon in virtual memory schemes when the processor spends most of its time swapping pages, rather than executing instructions. This is due to an inordinate number of page faults.

Interview Questions and Answers

7. What is a FIFO?
   FIFO are otherwise called as 'named pipes'. FIFO (first-in-first-out) is a special file which is said to be data transient. Once data is read from named pipe, it cannot be read again. Also, data can be read only in the order written. It is used in interprocess communication where a process writes to one end of the pipe (producer) and the other reads from the other end (consumer).
8. How do you create special files like named pipes and device files?
   The system call mknod creates special files in the following sequence.
   

   1. kernel assigns new inode,
   2. sets the file type to indicate that the file is a pipe, directory or special file,
   3. If it is a device file, it makes the other entries like major, minor device numbers.

   For example:
   If the device is a disk, major device number refers to the disk controller and minor device number is the disk.
9. Discuss the mount and unmount system calls.
   The privileged mount system call is used to attach a file system to a directory of another file system; the unmount system call detaches a file system. When you mount another file system on to your directory, you are essentially splicing one directory tree onto a branch in another directory tree. The first argument to mount call is the mount point, that is , a directory in the current file naming system. The second argument is the file system to mount to that point. When you insert a cdrom to your unix system's drive, the file system in the cdrom automatically mounts to "/dev/cdrom" in your system.
10. How does the inode map to data block of a file?
    Inode has 13 block addresses. The first 10 are direct block addresses of the first 10 data blocks in the file. The 11th address points to a one-level index block. The 12th address points to a two-level (double in-direction) index block. The 13th address points to a three-level(triple in-direction)index block. This provides a very large maximum file size with efficient access to large files, but also small files are accessed directly in one disk read.
11. What is a shell?
    A shell is an interactive user interface to an operating system services that allows an user to enter commands as character strings or through a graphical user interface. The shell converts them to system calls to the OS or forks off a process to execute the command. System call results and other information from the OS are presented to the user through an interactive interface. Commonly used shells are sh,csh,ks etc.

Interview Questions and Answers

1. Which TCP/IP port does SQL Server run on? How can it be changed?
   SQL Server runs on port 1433. It can be changed from the Network Utility TCP/IP properties.
2. What are the difference between clustered and a non-clustered index?
   1. A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages.
   2. A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.
3. What are the different index configurations a table can have?
   A table can have one of the following index configurations:

   1. No indexes
   2. A clustered index
   3. A clustered index and many nonclustered indexes
   4. A nonclustered index
   5. Many nonclustered indexes
4. What are different types of Collation Sensitivity?
   1. Case sensitivity - A and a, B and b, etc.
   2. Accent sensitivity
   3. Kana Sensitivity - When Japanese kana characters Hiragana and Katakana are treated differently, it is called Kana sensitive.