mLogica Thought Leaders: Refactoring Assembler to COBOL Seamlessly: Can You Automate Success?

Anthony Veltri, mlogica Senior V.P. of Solution Management


For decades Assembler code's ability to optimize hardware performance made it crucial to mission-critical applications running core business logic on mainframes. But now this low-level programming language has become a costly roadblock.

Assembler's platform-specificity, growing maintenance costs, and the dwindling pool of resources trained to run it means organizations are being forced to modernize to higher-level languages that offer more portability, scalability and efficiency. Migrating Assembler to modern languages such as COBOL, C# and Java enables private and public sector organizations to drive innovation by seamlessly and cost-effectively integrating advanced technologies into core business applications.

While many organizations prefer to refactor Assembler code directly to a more modern language such as Java or C#, there are situations when COBOL is a logical target. These include:

  1. Optimizing on the mainframe by consolidating existing languages to COBOL
  2. Leveraging current in-house COBOL expertise
  3. Choosing to replatform mainframe COBOL to a distributed environment, requiring the refactoring of Assembler to COBOL

If you're modernizing a mainframe system that includes Assembler code, and you’ve determined it does make sense to refactor to COBOL, there are challenges you’ll want to consider to ensure a successful migration. In fact, failure to do so can lead to the type of migration disasters far too many organizations have faced.

Converting apples to oranges

Assembler code and COBOL are fundamentally different languages with distinct syntax, data representations and control flow. Assembler code is a low-level language that deals with machine instructions, while COBOL is a high-level language with English-like syntax.

Converting such dissimilar syntax is a challenge, especially if this conversion is done manually. Using automated refactoring tools is the only way to ensure consistently accurate conversion—mandatory for a successful migration.

Assembler code can be found in application-oriented routines such as business logic, input/output instructions, datasets/databases access and more, and in system-oriented routines such as control blocks access for operating systems, dynamic datasets allocation, etc. An effective migration process relies on automatically converting Assembler logic into COBOL to ensure compatibility and functionality within the target system.

Assembler code often has direct dependencies on low-level hardware or operating system features such as endianness, bitness, encoding and more. When migrating to a COBOL-based system, these dependencies need to be handled with the utmost precision.

By using automated conversion software to refactor the Assembler code to COBOL you can identify alternative COBOL constructs or system interfaces that will interact optimally with your target system. Failing to address such dependencies often results in errors or unexpected behavior during the migration.

Refactoring Assembler code to COBOL requires a deep understanding of both languages, comprehensive assessment to determine the ecosystem’s unique requirements, and careful planning and testing. Leveraging automated conversion software ensures code compatibility with the target system, handles system dependencies, aligns data representations and improves maintainability. Neglecting this precision methodology can result in migration failures, including runtime errors, incorrect results and ongoing difficulties maintaining the migrated system.

Leveraging LIBER*M, our highly automated mainframe modernization software suite, mLogica moves your workload to the cloud in one-third the time and half the cost of traditional migration approaches.

For more information contact us at

Anthony Veltri, mlogica Senior V.P. of Solution Management