Programming

According to On becoming a quant by the late Mark Joshi:

All forms of quants spend a large amount (i.e. more than half) their time programming. However, implementing new models can be interesting in itself.

According to Steps to becoming a quant trader by Shobhit Seth:

Quant traders must be familiar with data mining, research, analysis, and automated trading systems. They are often involved in high-frequency trading or algorithmic trading. A good understanding of at least one programming language is a must, and the more programs the candidate knows, the better. C++, Java, Python, and Perl are a few commonly used programming languages. Familiarity with tools like MATLAB and spreadsheets, and concepts like big data and data structuring, is a plus.

According to What programming skills are needed in quantitative finance? on StackExchange:

In my opinion (and others will disagree I'm sure) to be a "world class" quant you need to have in-depth knowledge of a low level programming language (e.g. C++), working knowledge in a few high level languages (R and Python, for example), and strong working knowledge of SQL and databases.

According to Which programming languages will get you a job in a top hedge fund? by Sarah Butcher:

We looked at the CVs of 6,425 professionals working at 16 top hedge funds globally. Not all were following purely systematic strategies—some were multi-strategy funds. As the chart below shows, one language in particular features on the resumes of employees at top hedge funds: Structured Query Language (SQL). There's a reason for this: hedge funds which rely upon coding are all about devising trading strategies after collecting and analyzing huge data sets, and SQL is used within other programmes to modify and query databases. Ranking behind SQL are C++, Java and Python. They weren't nearly as popular in our sample and C++ was ahead of both Java and Python. Things might be changing though. Joel Sichel, a systematic trading headhunter at GQR Global Markets in New York, says that there's been a recent surge in demand for people who can code Python, "due to its transparency and ease of use for later users coming on to a pre-programmed system." This might be why Man Group's AHL Coding competition, in which student coders compete for a $5k prize, is again being run entirely in Python. SQL doesn't even get a look in.