<s>Human: 给定一个句子，将其中的每个单词的第一个字母大写。
hello world, how are you doing?
</s><s>Assistant: 可以使用Python语言来实现该功能，具体代码如下：

```python
sentence = "hello world, how are you doing?"
words = sentence.split()
capitalized_words = [word.capitalize() for word in words]
capitalized_sentence = " ".join(capitalized_words)
print(capitalized_sentence)
```

该程序首先将原始句子按空格分隔成单词列表，然后通过一个列表推导式将每个单词的首字母大写，最后将新的单词列表拼接成新的句子并输出。执行结果如下：

```
Hello World, How Are You Doing?
```
</s>