Fix typo in 4-application-development.md

data/part-10/4-application-development.md

@@ -680,7 +680,7 @@ The file handling process in the PhoneBook application proceeds as follows: the
 There are many good guidebooks for learning about good programming practices. One such is [Clean Code](https://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882) by Robert Martin. The code examples in the book are implemented in Java, however, so working through the examples can be quite cumbersome at this point in your programming career, although the book itself is much recommended by the course staff. The themes of easily maintained, expandable, good quality code will be further explored on the courses
 [Software Development Methods](https://studies.helsinki.fi/courses/cu/hy-CU-118024742-2020-08-01) and [Software Engineering](https://studies.helsinki.fi/courses/cu/hy-CU-118024909-2020-08-01).
 
-Writing code according to established object oriented programming principles comes at a price. You will likely end up writing more code than you would, were you to write your implementation in one continuous bout of spaghetti code. One of the key skills of a porgrammer is to decide the best approach for each situation. Sometimes it is necessary to just hack something together quickly for immediate use. On the other hand, if in the foreseeable future it can be expected that the code will be reused, maintained or futher developed, either by you or, more critically, by someone else entirely, the readability and logical modularity of the program code become essential. More often than not, if it is worth doing, it is worth doing well, even in the very early stages of development.
+Writing code according to established object oriented programming principles comes at a price. You will likely end up writing more code than you would, were you to write your implementation in one continuous bout of spaghetti code. One of the key skills of a programmer is to decide the best approach for each situation. Sometimes it is necessary to just hack something together quickly for immediate use. On the other hand, if in the foreseeable future it can be expected that the code will be reused, maintained or futher developed, either by you or, more critically, by someone else entirely, the readability and logical modularity of the program code become essential. More often than not, if it is worth doing, it is worth doing well, even in the very early stages of development.
 
 To finish off this part of the material you will implement one more larger application.