Master COBOL Interview Questions Essential Guide for Mainframe Developers

COBOL (Common Business Oriented Language) remains a foundational programming language in the business world, particularly in industries like banking, finance, and government. Whether you’re a seasoned COBOL developer or aspiring to enter the field, preparing for COBOL interviews is essential. In this comprehensive guide, we’ll explore the top 20 COBOL interview questions and provide detailed answers to help you ace your next interview.

COBOL, which stands for Common Business Oriented Language, is a high-level programming language primarily used for business, finance, and administrative systems. Developed in the late 1950s, COBOL remains prevalent in industries relying on legacy systems, such as banking, insurance, and government sectors. Its English-like syntax and extensive support for data processing make it suitable for handling large-scale transactional operations.

COBOL benefits programmers by providing a robust platform for developing and maintaining business-critical applications. Here’s how:

  1. Accessibility: COBOL’s English-like syntax makes it relatively easy for programmers to learn and understand, especially those with a background in business or finance.
  2. Robustness: COBOL is designed for handling large-scale transactional operations reliably. Its built-in features for file handling, data manipulation, and arithmetic operations ensure robust program execution.
  3. Compatibility: Many legacy systems and mainframe environments still rely on COBOL, offering a wealth of job opportunities for programmers with COBOL skills. Additionally, modernization efforts often involve interfacing with existing COBOL code, making it a valuable skillset.
  4. Stability: COBOL applications are known for their stability and longevity. Once developed and deployed, COBOL programs tend to run for many years without significant changes, providing job security for programmers specializing in COBOL.
  5. Industry Demand: Despite its age, COBOL remains prevalent in industries such as banking, insurance, and government, where reliability and scalability are paramount. Programmers proficient in COBOL can find lucrative opportunities in these sectors.

Top 20 COBOL Interview Questions and answers

1. What is COBOL, and why is it still relevant today?

  • COBOL is a high-level programming language primarily used for business, finance, and administrative systems. Despite being over six decades old, COBOL remains relevant due to its stability, reliability, and extensive use in legacy systems.

2. What are the divisions in a COBOL program?

  • COBOL programs are divided into four divisions: Identification Division, Environment Division, Data Division, and Procedure Division. Each division serves a specific purpose, such as identifying the program, defining data structures, and specifying processing logic.

3. Explain the difference between a level-number and a filler in COBOL.

  • A level-number indicates the hierarchical structure of data items in the Data Division, while a filler denotes a placeholder or unused area in a data record. Level-numbers range from 01 to 49, indicating data fields, whereas fillers are denoted by level-number 77.

4. What is the significance of the “Picture” clause in COBOL?

  • The “Picture” clause defines the format or structure of data items in COBOL. It specifies the type, size, and formatting characteristics of alphanumeric, numeric, and other data types, ensuring proper representation and manipulation of data.

5. How do you perform arithmetic operations in COBOL?

  • COBOL provides various arithmetic verbs like ADD, SUBTRACT, MULTIPLY, and DIVIDE for performing arithmetic operations on numeric data items. These verbs adhere to COBOL’s strict data typing rules and handle arithmetic exceptions gracefully.

6. What is the purpose of the “Perform” verb in COBOL?

  • The “Perform” verb is used for repetitive execution of sections or paragraphs within a COBOL program. It allows for structured looping and branching based on conditions, enhancing program readability and maintainability.

7. Explain the difference between “Call” and “Perform” in COBOL.

  • “Call” is used to invoke separate COBOL programs or subroutines, enabling modularization and code reuse. In contrast, “Perform” is used for repetitive execution of sections or paragraphs within the same program, facilitating structured looping and branching.

8. How do you handle file processing in COBOL?

  • COBOL provides file handling verbs like OPEN, READ, WRITE, and CLOSE for sequential and random access file processing. These verbs enable COBOL programs to interact with external files, such as reading input data or writing output records.

9. What are the different file organizations supported in COBOL?

  • COBOL supports various file organizations, including sequential, indexed, and relative. Sequential files are accessed sequentially from start to end, indexed files use a key to access records randomly, and relative files access records based on their relative position within the file.

10. How do you handle error conditions in COBOL?

  • COBOL provides error handling mechanisms like condition-names, “On” statements, and the “Handle Condition” phrase for graceful error handling. These mechanisms allow COBOL programs to detect and respond to error conditions effectively, ensuring robustness and reliability.

11. What are the different data types supported in COBOL?

  • COBOL supports various data types, including alphanumeric, numeric, and special data types like packed-decimal and binary. Alphanumeric data types represent characters and are defined using the “PIC X” clause, while numeric data types represent numbers and are defined using the “PIC 9” clause.

12. How do you define arrays in COBOL?

  • Arrays in COBOL are defined using the “OCCURS” clause within the Data Division. The OCCURS clause specifies the number of occurrences or dimensions of the array and allows for efficient storage and manipulation of repeated data elements.

13. Explain the concept of “REDEFINES” in COBOL.

  • “REDEFINES” allows data items to share storage space with another data item, enabling multiple interpretations or views of the same memory area. It is often used to represent the same data in different formats or to overlay data structures for efficient memory utilization.

14. What is the significance of the “88 level” in COBOL?

  • The “88 level” in COBOL is used to define condition-names, which represent specific conditions or states within a data item. Condition-names provide a symbolic representation for boolean conditions, enhancing program readability and clarity.

15. How do you perform string manipulation in COBOL?

  • COBOL provides string manipulation functions like STRING, INSPECT, and UNSTRING for manipulating alphanumeric data items. These functions enable tasks such as concatenation, search and replace, and parsing of strings within COBOL programs.

16. What is the difference between “Static” and “Dynamic” linking in COBOL?

  • “Static” linking involves linking external subprograms or modules at compile-time, resulting in a standalone executable file. In contrast, “Dynamic” linking occurs at runtime, allowing for the loading and execution of external modules as needed, enhancing flexibility and resource utilization.

17. How do you handle date and time operations in COBOL?

  • COBOL provides intrinsic functions like CURRENT-DATE and DATE-OF-INTEGER for working with date and time data. These functions enable tasks such as obtaining the current system date and time, calculating date differences, and formatting date values as needed.

18. What are the different types of COBOL statements?

  • COBOL statements can be categorized into four types: executable, declarative, compiler directive, and identification. Executable statements specify processing logic, declarative statements define special processing conditions, compiler directives provide instructions to the compiler, and identification statements identify the program and its components.

19. How do you handle null values or uninitialized data in COBOL?

  • COBOL provides the special value “NULL” to represent null or uninitialized data items. Programmers can check for null values using conditional statements or special COBOL verbs like “IS NULL” or “IS NOT NULL” to handle such cases gracefully during program execution.

20. What are the considerations for migrating COBOL applications to modern platforms?

  • Migrating COBOL applications to modern platforms involves considerations like assessing legacy code compatibility, identifying dependencies, redesigning user interfaces, and ensuring data migration and integration with modern systems. Tools and frameworks are available to facilitate smooth migration while minimizing disruption to business operations.

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By delving into these additional COBOL interview questions and their answers, you’ll deepen your understanding of COBOL concepts and techniques, preparing you to tackle a wide range of interview scenarios. Stay curious, keep exploring, and leverage your newfound knowledge to excel in your COBOL career journey.