How Handwritten Code Shaped Early Programming: Insights from Margaret Hamilton and Beyond

Handwritten code played a crucial role in the early days of computing, laying the groundwork for modern software development. This essay explores the process of handwritten code through the eyes of Margaret Hamilton, a prominent figure in the Apollo space program, and draws on personal experiences from the 1970s to understand the challenges and techniques involved.

Introduction to Handwritten Code

During the early days of computing, programming techniques were rudimentary compared to today’s sophisticated tools. Programmers often used handwritten code as a means to create, test, and debug software before it could be input into early computers. While the methods have evolved, understanding these early practices provides valuable insights into the evolution of software engineering.

How Margaret Hamilton Handwrote Her Code

Margaret Hamilton, a renowned computer scientist, was instrumental in developing the onboard software for the Apollo space missions. Her experience with handwritten code was pivotal in the success of these missions, setting a standard that would later influence modern software practices.

Using Paper and Notebooks

Programmers like Hamilton typically used lined or graph paper to write their code in a structured format. This method often resembled the syntax of the programming language they were working with, making it easier to understand and follow.

Notation and Comments

Handwritten code included notations and comments to explain the logic and flow of the program. This was particularly important for readability, especially when sharing or revisiting the code later. Detailed comments helped ensure that the code could be easily understood and maintained.

Punch Cards

After writing the code, it was often transferred to punch cards. Each card represented a line of code, and these cards would be stacked in order. This method provided a physical medium for storing and transferring code, which was crucial before the advent of digital storage.

Error Checking

With no immediate way to test handwritten code, programmers had to meticulously check their work for errors. This involved careful proofreading and sometimes peer reviews to ensure the accuracy of the code before it could be input into the computer.

Iteration

Handwritten code allowed for easy modifications. If a programmer needed to make changes, they could simply cross out or rewrite sections of code on paper before transferring the final version to punch cards. This flexibility was invaluable for iterative development processes.

Collaboration

In team settings, programmers often collaborated by sharing handwritten notes and code snippets. Discussing logic and design iteratively allowed for collective refinement and improvement of the code. This collaborative approach was essential for successful projects.

Personal Experiences in the 1970s

While Margaret Hamilton’s work was critical for the Apollo missions, stories from the 1970s provide additional context to the challenges faced by early programmers. One such experience involved writing software for an embedded 8086 processor.

The operating system was written in assembler, which posed no problem since the tools were available to convert input into machine instructions. However, the 8089 DMA co-processor required a custom assembly language for which no tools existed. The process of designing the program and manually converting it to machine instructions by writing in hex was a significant challenge.

Challenges in Handwritten Code

One of the difficulties was with relative addressing. Any additions, deletions, or changes to instructions between a jump instruction and the destination required recalculating the offset. This manual calculation was labor-intensive and prone to error.

Testing and Debugging

Once the code was written, it was included in the operating system as a data block. The development process, including testing and debugging, took about 10 days. Despite the limitations, the experience reinforced the importance of careful planning and iterative refinement in software development.

Conclusion

Handwritten code was a fundamental part of early computing, shaping the methods and practices that would eventually evolve into modern software engineering. Margaret Hamilton’s contributions and personal experiences from the 1970s illustrate the challenges and coping mechanisms of early programmers, providing a rich history of how code was written, debugged, and deployed before the advent of modern tools and methodologies.