Stocks staged a broad rally to cap off a strong week. The Dow Jones Industrial Average (DJINDICES:^DJI) ended at session highs today, gaining 397 points, or 2.5%. The S&P 500 (SNPINDEX:^GSPC) added 47 points, or 2.5%.

^DJI Chart

^DJI data by YCharts.

Investors reacted positively to news that central banks around the world appear willing to do whatever is necessary to keep global growth from slipping back into negative territory. The Bank of Japan became the latest example of that willingness, as it set its short-term interest rates to below zero for the first time.

Earnings results also grabbed the attention of investors, with tech giants (NASDAQ:AMZN) and Microsoft (NASDAQ:MSFT) both making large moves today after posting their fourth-quarter numbers ahead of the opening bell.

Amazon's runway for growth
Amazon fell 8% following its fourth-quarter earnings announcement last night. Yet that seemingly dramatic slump only left shares at roughly even for the week, and still up 88% in the last year. The stock jumped 9% yesterday before giving back most of that gain in today's session.

Despite missing consensus estimates by a tad, the Q4 numbers were impressive. The e-commerce giant's revenue rose 22% -- or 26% on a currency-neutral basis -- and net income jumped to a record $595 million compared to a $241 million loss in the prior-year period. The company passed $100 billion in annual sales, and now counts more than 300 million customers.

Image source: Amazon.

Amazon made encouraging progress in boosting its services division, as its AWS cloud segment posted a 69% revenue spike. Profitability rose even faster, nearly tripling on an absolute basis, as segment operating margin expanded to 29% from 17% last year.

The company provided a wide range of possibilities in its official forecast for Q1, saying sales could clock in as low as $26.5 billion, or as high as $29 billion. Operating income will be between $100 million and $700 million, which would represent either a 61% decline -- or a 175% increase -- over the prior year's haul. CEO Jeff Bezos focused on the long-term outlook, saying in a press release that the "ever-expanding opportunities we see to invest on behalf of customers" give executives confidence that there's a long runway for growth ahead.

Microsoft's growing cloud business
Microsoft was the best-performing stock on the Dow after logging a 6% pop, and nearly setting a new 52-week high. The software giant announced fourth-quarter results that beat expectations as sales ticked lower by 2%, to $25.7 billion, and adjusted earnings rose 11%, to $0.78 per share. Consensus estimates had called for $25.3 billion in revenue and $0.71 per share of profits.

Image source: Microsoft.

A large improvement in its cloud segment helped offset continued weakness in the personal-computing division, which fell 5% on soft Windows demand. Yet that decline still beat the broader PC market, which fell by 8%.

In contrast, Microsoft's cloud-services business posted strong growth. It reached a $9.4 billion annualized rate -- up from $8.2 billion in the third quarter, and the Azure portfolio showed particular strength, growing 140%, year over year. "Businesses everywhere are using the Microsoft Cloud as their digital platform to drive their ambitious transformation agendas," CEO Sayda Nadella said in a press release.

Microsoft's outlook for the current quarter pegged revenue at slightly less than the $22.3 billon that analysts were targeting, yet it still represents 3% growth over the prior year.